Frank Snepp doesn't call them nightmares: soundmares is the word he uses.

"I wake up in the middle of the night," he says, "and I hear radio transmissions from the last day we were there; people are screaming. I have to carry Duradyne (a narcotic more potent than codeine) with me all the time.I sleep maybe three hours a night."

Frank Snepp was the CIA's chief strategy analyst in Vietnam. Last week Randem House published his 600-page account of America's most disastrous mistakes in Vietnam and Southeast Asia. Since then, he says CIA folks have been tracking him down and calling him up and telling him he's a traitor. And the media - newspapers, magazines, "60 Minutes" - have been trailing after Snepp and his story.

"I wrote this book to exorcise the ghosts," Snepp says.

Like the one that came traipsing through his room one night in Saigon.

"I had an M16, a .45, a .38, a hand grenade and a carbine under my bed," he says, "I had been taking malaria pills and drinking martinis. It did something, and one night I woke up and I though somebody was walking across the room, and reached for the f . . . carbine and I blew the air conditioner right out of the wall."

Snepp tells lots of stories with that I've-been-there-so-you - better - believe this look. "Another time I was in a bar in Saigon with a friend and two Vietcong guys came in and started shooting and I flipped a whore over my shoulder and ran up into one of the rooms upstairs. They hit her in the leg and there was blood streaming out of her and she said to me. "Your friend is still out 'here.' So I went out and the two guys and we just beat them to death right there on the spot. I mean, we battered them to death."

Death is but a fragment of Snepp's book. "Decent Interval," which is filled with outrageous tales of bureau cratic bunglings; how facts that didn't jibe with what Washington wanted to hear were revised to tow the line; how other facts were changed to give the impression that a few more billion dollars could win the war; how Henry Kissinger was duped by Soviet diplomats into thinking that Hanoi would never invade Saigon; how thousands of Vietnamese recruited for the American cause and thousands of CIA files were abandoned in the mad rush to clear out of the collapsing capital.

Virtually all of the American officials named in Snepp's accounts - Kissinger, Ambassador Graham Martin, former CIA director William Colby and CIA station chief Tom Polgar - have already taken exception to Snepp's version of the events concerning themselves.

In revealing all this, the 34-year-old former analyst violated a written pledge made by every CIA employee to clear anything said or written about the agency with the front office. Snepp claims that his resignation in January 1976, came only after his supervisors had resisted efforts to get an in-house investigation under way. He then announced that he had thoughts about writing a book, but left the specifics vague.

Then the weirdness really started. Meetings with editors in Manhattan parks. An argument with a neighbor in Arlington: The guy liked to play rock 'n' roll LOUD in the afternoons, even as Snepp was squawking his memoirs into a tape recorder, which would not do. Flying fists, and the guy moved out of the apartment.

At the Fun & Fitness Health Club on Lee Highway, geriatric ladies looked at him strangely, he says, when he showed up to swim every afternoon for 18 months, looking like some unemployed bum. His colleagues at the CIA avoided him like swine flu, for the most part. And, of course, Snepp was convinced that his phone was bugged. He'd take his tapes to New York to be transcribed by an out-of-work actress he knew. His phone conversations began to sound like CIA standards. His editor, Robert Loomis, became Janice. "Has Janice put the apartment together yet and has she done anything about the curtains?" meant simply "What's up with the maps in the book?"

Meanwhile, at Random House, perhaps a dozen of the company's 800 employees knew that the book was being published. Largely because in 1972, Knopf's battle with the CIA over "The CIA and the Cult of Intelligence" by Victor Marchetti and John Marks cost Knopf $150,000 in legal fees, Snepp's book that didn't exist.

Various parts of the text were shipped out to different typesetters. No galley proofs were made. The individual letters for the cover copy ("An Insider's Account of Saigon's Indecent End Told by the CIA's Chief Strategy Analyst in Vietnam") were ordered separately. And on the night before the cover deadline the copy was handed to the art director with instructions on how to assemble the letters. Snepp's mother made sketches of the characters for the book's title pages, never knowing precisely what the book was about. Snepp did not pay his 1976 income tax on his less than $50,000 advance, for fear that the CIA might discover who his publishing house was. Finally the books were shipped last week to stores that didn't even know the book existed - with a letter explaining what was going on.

Snepp comes on like a nasty spook on the outside. He wears a black leather overcoat, tough-guy boots and a Clint Eastwood face, and carries a slim little black attache case and a bulging brown Jiffy bag. Back in Saigon, acquaintances say, he used to push the bar girls aside with his attache case and carry a .45 in a brown paper bag. Now he'll only say that his pain pills are in his case. He passes on vension at LePavillon, a swanky downtown French restaurant because, he says, he has an incredibly delicate stomach.

"I had a IY classification for the draft (only available for national emergencies), and that was very embarrassing," he says. Two drinks later he admits that he has colitis - "a very embarrassing disease." And he says that he joined the CIA basically to avoid the draft.

Frank Snepp grew up in North Carolina and says he never heard of the CIA until he went off to college - in spite of his judge father's friendship, long ago, with William Colby. In fact, Colby was scheduled to be young Snepp's godfather but didn't because of some now-forgotten snafu.

Snepp says he didn't know of his father's friendship with the former CIA director until he returned from his 1969-71 tour of duty in Saigon. (Snepp later returned in 1972 and stayed until the collapse in April 1975.)

At Columbia, Snepp majored in Elizabeth literature, graduated in 1965 and worked for one year with CBS News as a copy writer, then returned to Columbia for a masters degree in 1968.

"I graduated the same year that Mark Rudd started tearing that campus down," he says, "and that bothered me."

Just before graduation, Snepp was recruited by the CIA, which appealed to him in part, he says, because of his love of James Bond novels.

"I was at the Columbia School International Affairs," he says, "and I thought I'd like to go into the State Department. A professor there, who was recruiting for the agency, told me I wasn't quite quick enough for Stare, but I'd do well in the CIA. And he knew that the one thing I didn't want was to get my a -- shot off on some front in Vietnam."

"So he told me that the CIA would arrange to get me enrolled in some bogus R.O.T.C. program, and I wouldn't get out of the draft by joining the CIA, but they could take care of anything they wanted to. I was working in Langley and they had sent out some request for somebody to go to Saigon. Some friends applied for means as a practical joke.

"I got picked for the job and walked into an interview and tried to talk my way out of it, and they convinced me to do it, that it would be perfectly safe. So I went through all those machinations to avoid the place, and wound up going there anyway."

Which may, in fact, be the perfect expression of the paradox that plagues Frank Snepp. On the one hand, he believes in the CIA, and the ways that the CIA can teach you to twist the truth. On the other hand, he says he has a "moral question" with the agency - something he well realizes might be construed as a bit of truth twisting in itself.

"I am a disquieted Quiet American," Snepp says. "But I'm willing to take the consequences. Philip Agee (author of "Inside The Company: CIA Diary"), that son-of-a-bitch. He runs away from the country for asylum and then blows the cover of a lot of working agents. At least Marchetti and Marks submitted their book to the agency, although they still blew some covers. I was very careful to protect people. If you have a moral gripe to pick, you do it on moral terms. If you believe in something, you act like Martin Luther King and stick around for the consequences."

Then too, Snepp did not submit his book to anyone at the agency because, as he rationalizes it, the CIA had blown its end of the secrecy pledge by leaking half truths to the press.

He likes to cite what's chisled into the building hall in Langley: "Ye shall know the truth and the truth shall make ye free."

"I didn't mind putting people through hard times as long as the truth came through," he says. "During Operation Phoenix, I gave the Saigon military a lot of names of people I wanted killed. But I found out that the truth wasn't going to make anybody free because it wasn't getting back to Washington."

For Snepp, the truth he writes about was found in an arena bounded by the blazing Asian sun and fortified CIA compounds, leavened occasionally by the silken charm of Saigon, sharpened by the fierce combat of interrogating a prisoner from Hanoi in a frigid white chamber, honed by the endless hours of evaluating charts, studies, lies and betrayals.

Guilt broods in Frank Snepp. One of the people the book is dedicated to, Mai Ly, was a woman who ran an orphanage for illegitimate children of American servicemen.

"She killed herself," he says. "She called me up the morning of the evacuation, and I told her I was too busy to talk, and that I'd call back. I never called her back, I was just like TOm Polgar, who postponed the evacuation. I postponed helping that woman, and now she's dead because of it."

Snepp is not the most optimistic guy in the world these days. There are, he concedes, a few rewards for the Savonarolas of Spookdom.

"I see nothing in my future," he says. "Random House is talking about a novel, which I think is a joke. This book probably won't really sell that well. I'm not a great writer. I mean, I read parts of Michael Herr's 'Dispatches' and I wish I could write like him. I don't think any newspaper would be willing to hire a former agent who broke his word with the agency. I've eaten up my advance and all my savings from my $25,000-a-year CIA job. I'm gonna be out playing bartender soon."

Which reminds him of the upshot of the Saigon barroom shootout he says he was involved in.

"The next day I walked in the bar, and they were all calling me a hero. And I ordered a scotch and water, and the bartender said, '$1.50, please.' The big hero didn't even get a free drink."