The words are pouring out of Richard Thomas' mouth.

"As an actor you want to know you've worked hard and that you've arrived," he is saying. "And then when you've arrived, you want to think that it's never going to change.

"So you erect this edifice around yourself, and it's a perfectly natural thing to do. You're just protecting yourself, because to be an actor means that you must be given permission to work. You're constantly in a posture of supplication. Constantly. I mean, I spent my entire childhood working as an actor. I auditioned for everything. I got up and did whatever they asked me to do. I went out on the stage of those dark theaters and sang and read those scenes, and believe me, at the age of 10, 11, 12, that can be a very terrifying experience.

"But I did all that. And then you get to the point where you think you have a position, a job, a reputation, and you say to yourself, 'I don't ever want to go through that again. I don't have to put myself through that humiliation. I've paid my dues.' And that's an incredibly dangerous crossroads. Because that's the day you decide your own security is more important than the impulse to be an actor."

There is, in the rush of words, an urgency bordering on obsession, as if Thomas is afraid the tape recorder whirring before him will click off before he's down on record. Not as TV's John Boy or People magazine cover boy or even the nation's best-known father of triplets, but as an actor to be taken seriously. An artist!

"I remember when I came off 'The Waltons,' and it was, you know, a top-rated show, and TV movies were being made for me. There's no corner of the globe they don't know 'The Waltons.' I'd had Masai chase me in Kenya. Boatloads of Greek schoolgirls. Kuwaiti tourists in London. I still get mobbed at places like the circus or Disneyland, where there are families and large groups of children. It is almost impossible to overestimate the power of a successful television role in terms of what it implants in the minds of the audience.

"When you're in a hit TV series, you become a king. King of the set, king of the studio. You've got your own parking space. Everybody's a colleague. On weekends, I kept an open bar at a restaurant in L.A. for the crew of the show. If I'd say to the directors, 'Hey, my character wouldn't do this!,' they'd say, "Yeah, sure, Richard, sure, that's okay.' You feel . . . impervious. I did. I felt impervious.

"Anyway, after five years, I left the series and I was doing a stage production of 'Streamers' in L.A., and I suddenly became aware that I was surrounded by young, angry, anxious actors. I mean these were hungry guys, who were going to get parts because they needed them. And the only reason I was going to get parts was because of this position I had, which is no reason at all. I used to watch them on stage every night, and it was scary. And I said to myself, 'You'd better kick all the crap out of the way.' You know, all the stuff that feeds the illusion that there is security in this business. Because it is an illusion. There is no security. You've got to kick it away and get hungry again. And you've got to stay hungry. It's as simple as that."

Or as complicated. Richard Thomas is not a quiet soul.

As Edmund Dantes, "The Count of Monte Cristo," Thomas is a key player in the second production of the American National Theater, which opens Saturday in the Eisenhower Theater. In terms of sheer length, the role may well be the biggest of Thomas' career -- three hours of towering melodrama that require him to go from innocent youth to bitter middle-age by way of all the elaborate conspiracies, sinister betrayals, dank dungeons and storm-tossed seas so beloved of 19th-century theater. ANT, which debuted miserably earlier this spring with "Henry IV, Part I," has a lot riding on him, too.

Today, "The Count of Monte Cristo" is largely remembered as the vehicle that brought fame and fortune to James O'Neill (the father of playwright Eugene O'Neill), even as it typecast him to the end of an increasingly alcohol-soaked career. ANT is using O'Neill's own acting version, although it has been filtered through the decidedly avant-garde sensibility of director Peter Sellars -- and acquired, in the process, chunks of dialogue from the Bible and Lord Byron. Still, Thomas is not exactly what they call in the trade "dead-on casting."

"Can you think of a better reason for me to do it?" the actor says. "More than a type, what the role requires chiefly is an actor who can accomplish it. It's enormous, extremely demanding. There are five acts and in each act, Edmund Dantes is almost a different person. Type has little to do with this production anyway, being that Peter is directing it. Why would the obvious choice spring to his mind, although, frankly, I don't fancy myself a perverse choice."

The public at large, of course, continues to view him as John Boy, that flaxen-haired paragon of rural decency. He stayed with "The Waltons" for five seasons (1972-77), then dropped by for the occasional guest appearance until it left the air in 1981. Reruns have kept it alive ever since. Thomas is now 33 and the angelic cast of his features has barely hardened. Two years ago, he discovered that he was having vocal problems. A doctor ("the same one that the gentleman in the White House has") traced it to the fact that he was losing his hearing and as a result overcompensating with his voice. The loss has been arrested, but without the tiny transistorized aids he wears in both ears, he hears only 50 percent of what he used to. Otherwise, the signs of aging are imperceptible. Passers-by in the street recognize him instantly.

For some, John Boy was virtuous to the point of goody-goodness, a milquetoast in Depression rags. But not for Thomas. "John Boy was a wonderful kind of eager, naive, foolish, impetuous young man," he says. "If he arrived at his good decision-making and his right choices, it was after a great deal of conflict. That was true of all the characters. 'The Waltons' really was a critically important show. It was aired in the midst of the most alienated period of American television. The dramatic shows that were on the air then were tough, strong shows like 'Mod Squad' and 'Kojak.' The comedies were filled with bitterness and disappointment, a sense that America was falling apart, that people mistrusted one another, that older people were forgotten. Then along came this show, which reaffirmed the faith in the family unit as something important and healing. John Boy was a powerful icon of a kind of American youth, a brother figure, the kind of son parents would like to have. I have no desire not to be remembered for that show."

Nonetheless, the actor in him knew that if he didn't want to be pegged forever as Boy Wonderful, he had better move on. "They didn't believe me at the time," Thomas says. "They thought it was a renegotiation ploy and offered me more money. But it wasn't. I think I sensed, rightly, that balancing the scales in terms of the public's perception of me as an actor was going to require at least as much time as I had put into that show. And very likely more."

In 1981, Thomas returned to Broadway for his first New York performance since he was 16. Shunning a star vehicle, he agreed to replace Christopher Reeve as a paralyzed homosexual Vietnam veteran in "The Fifth of July." He had four rehearsals beforehand, only one with the full cast, and triumphed. "Thanks to a major casting change . . . the full beauty of this comedy has finally been uncorked," Frank Rich wrote in The New York Times. "The difference is Richard Thomas . . . who not only gives a performance that gracefully builds to shattering dimensions, but has also sparked the rest of the company to follow suit."

Thomas has since appeared off-Broadway in "The Seagull" and in such made-for-television films as "All Quiet on the Western Front," "Hobson's Choice," "The Hank Williams Jr. Story" and "The Master of Ballantrae." This summer, he will repair to the Williamstown Summer Theatre Festival, where he will be "Tom Paine" in the theater's studio for works in progress. Ninety spectators a night will be watching, as opposed to the millions who tuned in to the series. Thomas doesn't consider it a comedown.

"Every job I do is an artistic fix I need," he says, the voice gathering intensity again. "Theater is not a part of my life I have ever questioned. I ask myself the opposite question, 'What would I do if I didn't have theater?' It's a great rock. I really believe that the most important thing in the building of a career is time -- a slow, gradual accumulation of a body of work that stands by itself.

"What I know is that success is comprised of all the elements that have gone before it. And if there are successes, there will be failures, and the failures will be hard to take, and the successes will be hard to manage. But you must make time your ally. If you truly feel you have a gift and a sense of worth about yourself and you persist, time will give you another chance. You'll go up, you'll go down. There will be periods when you have no job, and periods when you can't do all the work that you want to do. It's all going to happen to you. Nobody lives a completely charmed life."

There is, if not an element of charm, at least backstage magic about Thomas' upbringing. His parents were dancers with Alicia Alonso's ballet troupe in Cuba -- "I was the company mascot," he jokes -- and Spanish was his first language, until the family moved back to Manhattan. Having working performers as parents, Thomas grew up naturally "feeling part of a theater world, bigger than you, populated by ghosts and traditions, greater than you." His sister took up ballet, but Thomas says, "I think my parents sensed that I had too big a mouth to be a very good dancer. I'm verbally oriented, although I'm built exactly as Nijinksy was. I've known members of his family for years, and that's what his sister and niece say."

It was, however, his first-grade teacher at a straight-laced East Side private boys school who got him started in theater. A children's agent in her spare time, she took Thomas to audition for the role of John Roosevelt in "Sunrise at Campobello." He got the part; at age 7, he was on Broadway and loving it. Subsequently, while playing John Henry in an Equity Library production of "Member of the Wedding," the realization hit. "That's a great part for a child actor to find himself in, and one night in the second act, as I was sitting there, I suddenly said to myself, 'You're acting!' Not: 'You're out on a stage and you've got to remember your lines.' But: 'You're acting. You are an actor!' Ever since that night, I've known that's what I do. Once it's there, it's there forever."

His parents put the brakes on his career only once. He was 10 and auditioning for a commercial for Greyhound buses at "one of those cattle calls for kids, which are really depressing," he recalls. "My dad was there and the casting people came up to him and said, 'You know, he really is a nice boy and he has a nice quality. But if you ever want him to work in this business, you must have that birthmark taken off his face. It's just going to be a terrible handicap.' And my father said 'Thank you very much' and turned and walked away. I was never sent up for another commercial. 'If that's all they're looking at,' he said, 'you don't have to do that again.' It's funny. People must notice it, but it's never gotten in the way since. I've always considered it to be good luck."

Before long, Thomas was working regularly in live television (Hallmark Hall of Fame, Du Pont Show of the Month, Armstrong Circle Theatre) and theater (the Actors' Studio legendary 1964 revival of "Strange Interlude," Edward Albee's "Everything in the Garden"). Hollywood latched onto him starting in 1968, when he was cast as Paul Newman and Joanne Woodward's son in "Winning."

"Any time I look at pieces of my work from then, all I see are tears and quivering, just this mass of undisciplined feeling," he says. "From the age of 16 to 24, I was forever playing sensitive young men going through the rites of passage. I was forever discovering manhood. I don't know how many times I reached manhood. Many people think I still haven't reached it."

He was a shoo-in for John Boy.

In the world of show business, it takes a lot to turn an image around. Cher had to remove her makeup, don ratty clothes and play a lesbian in "Silkwood." Lena Horne shucked her sophisticated supper club style and got down and dirty in a one-woman Broadway show. In Thomas' case, his Mexican-American wife, Alma, gave birth to triplets -- doubling the size of the household overnight. (Thomas and his wife also have an 8-year-old son, Richard Francisco.)

The triplets -- a 9,300-to-1 chance, as People magazine dutifully reported -- were born in August 1981, while he was appearing in "The Fifth of July." His sterling notices were all but lost in a tidal wave of publicity about the number of Pampers that Barbara Ayala, Gwyneth Gonzales and Pilar Alma were going through per week; their special diet of fresh fruits and vegetables, processed in the Cuisinart; their rotating baths in the kitchen sink; their respective weights, sleeping habits, personalities. Everything, it seemed, but their career ambitions.

The all-American boy had suddenly become the all-American father. "People used to come up to me and ask, 'What are you doing? I saw your last picture, it was great, and I loved the series,' " Thomas says. "Now they ask, 'How's your wife and how is she coping? Is she okay? And the little girls? How's your son? Oh, and by the way, have you done any work lately?'

"I've never had the kind of image that makes people want to run up and tear my clothes off and scream and carry on. But now, they approach me with very specific questions about the logistics of raising triplets. Well, that's great, it allows you to discuss the one thing that Emily Post says you're not supposed to talk about in polite society -- your children. But I'm telling you, my wife eclipsed my entire professional accomplishment in one fell swoop. It's really justice, isn't it! All the slowly accumulated pieces of work, carefully put together over the years, just tumbled apart at that moment. I think that's the ultimate show business stunt on her part. Really, the perfect actor's spouse's revenge."

These days, you can even see Alma and the tots, alongside Thomas, in television spots for Minute Maid orange juice -- the first commercial endorsement the actor has undertaken since the Greyhound bus passed him by. He calls it "manna from the Coca-Cola company," which apparently considers him and his brood a worthy successor to that former ideal of orange-drinking togetherness, the Bing Crosby clan.

"It's very simple: The kids are running around and my wife is pouring orange juice and I'm drinking it. We're kind of a mess, just as we are as a family," Thomas says. "I certainly didn't go looking for it. But it allows us to work together, and the kids are earning money, which is put aside for them. And selfishly, it allows me the freedom to pursue the kinds of roles that I want to do without having to worry about the bucks. I'd rather make money selling a product that is wholesome than have to call up my agent and say, 'I need a two-hour movie, quick,' and have him say, 'Well, the only thing they're doing on CBS is 'Lace XII.' And then think, 'Well, I guess I'd better take it.' "

Still, if fatherhood has added a dimension to Thomas' persona, it has not significantly altered it. After all, triplets, a Great Dane romping in a sun-drenched California back yard and cross-country trips in a Ford van, packed to overflowing, are pretty much what America expects -- and wants -- of its John Boys, when they grow up. Although Thomas boasts cheerfully that "I am easily the most domestic actor you'll meet" -- the domesticity does not entirely conceal the subterranean depths.

Ask him if he's square and he shoots back, "I don't think anyone who has spent 27 years in the theater as a working actor can be considered square."

So what is his most exasperating trait?

"I have a lot of energy . . . well, it can get in the way. This ingenuous, superenergetic appearance exasperates people. I have to make myself slow down in order to function more effectively. Of course, I'm convinced it's all going to fall apart overnight. I'll wake up and I'll look in the mirror and it will be gone. I'll go from playing 25-year-olds to 65-year-olds in one day."

He laughs, but the laughter is only a brief interlude before he concedes, "You know, I am an intensely moody person. I mean, I have a truly Celtic disposition. I'm a quick reactor and I have a short temper, a Welsh temper. I am strict with my children. And, being an actor, I have that peculiar chameleonlike personality which takes on the color of its environment. I suppose that looks like a form of insincerity to some. I can only hope it isn't. I don't think it's an accident that my performance in 'The Waltons' was so real to people; the values in that show were values that I espouse and that are part of my life. Family and work are of primary importance to me. But there's also that part of me that allows me to play the vengeful, spiteful, angry, loveless Edmund Dantes at the end of 'The Count of Monte Cristo.' "

"I happen to believe that acting involves dangerous risks. The chemist works with very dangerous materials. So does the actor, only the actor can't take his elements and put them in a closet and lock the door when he's through. They're ever-present, in you at all times. You must treat them as carefully as a person working in a laboratory treats his materials so that you can call them forth and suppress them as required. Otherwise, you can become a ganglion of conflicts without gravity, without a center."

The words are beginning to build again with the passion of a monk proclaiming his credo to the infidels. Only in this case, the infidels are unseen moguls, myopic casting directors, the executive pillars of a business that thinks it knows who Richard Thomas is and what he can do.

"I know I can play anything I like," he's telling them. "I can play male, play female, play good, play bad, play tough, play soft. Anything! Because if you don't believe you can do it, then you really don't believe you're an actor."

And Richard Thomas is a true-blue believer.