"Let's say there are 332 people who control the United States." Richard Condon isn't sure about the exact figure, but has no doubt about the fact. That's one of the reasons he has lived outside his native country for the last 26 years.

Condon, 64, one of the primary beneficiaries of the conspiracy theory of American politics, is also a true believer. Since the publication of "The Manchurian Candidate" in 1959, he has become a wealthy best-selling author by giving readers the uneasy feeling that The Government Isn't Telling Us Everything. Subsequent events, including the Kennedy assassination, the Vietnam escalation and Watergate have reinforced both his thesis and his bank account.

After working for 22 years as a publicity agent for Walt Disney, Condon began writing fiction in the '50s.

Of his 18 novels, half deal with American politics, six have been sold to filmmakers and four have so far been filmed. He likes the new film of "Winter Kills," which deals with the Kennedy assassination, upholds the hotly debated theory that a second gunman was involved, and portrays a Joseph Kennedy-like figure behind the death of the president.

Sitting in his suite at the Madison, puffing on a cigar that his wife would not let him smoke at home in Ireland, Condon returns again and again to the hidden powers that he believes manipulate our destinies:

"It doesn't really matter who killed Kennedy or who killed Abe Lincoln - they're dead. What matters is that the manipulators are so powerful they can have someone like that killed because he's bad for business."

Business and politics: In another novel, "Mile High," Condon suggests that a consortium of businessmen manipulated the United States into prohibitian for their own financial gain.

Condon was in Washington almost by accident. He had to come to New York to deliver the manuscript of his next novel on time. "It's called 'The Entwining,' and I guess you could call it a melodrama about the Equal Rights Amendment," he said "I had to fly over with it because there is a postal strike over there - including telephone, telegraph and telex. When I want to communicate with my wife, I have to do it by courier."

Most artists and writers who emigrate to Ireland do so because of tax incentives - Ireland charges no taxes on income derived from artistic activity. But Condon has retained his American citizenship and still pays American income taxes.

"What bothers me," he says, "is not that I'm paying taxes,but that I'm paying them to the wrong government. I don't use American roads, and I certainly don't want to use the American Army. But I am paying for them - and Ireland needs the money."

Despite the difficulties, he finds Ireland congenial: "It's so peaceful. We have a very old house designed by James Hoban, who also designed the White House, and from our front door you can see 60 miles of Kilkenny and Tipperary with nothing moving but cows and an occasional Guinness salesman.

"Ireland is our seventh country and we've lived there for eight years - moved from Switzerland. I think Switzerland is our favorite country, but even David Rockefeller couldn't afford it.

"Ireland is the least crowded country in Europe. The only crowded places are churches, bars and racetracks."

Condon's visit coincides with the long-delayed release of the film version of "Winter Kills." Describing it, he sounds like a proud parent:

"When my other books were made into movies, I would see them once and then forget about them. I figured they were someone else's problem. But this one I have seen twice, and my total satisfaction is based on the fact that the producers go for broke. They didn't evade the opportunity to malign authority. The movies goes several steps beyond my novel, and it's the first movie I've seen that really deals with the American culture of money and manipulation. It's a hard, dirty, sinister book and movie."

Not surprisingly, Condon makes the story sound like another conspiracy: "When the book came out, it was well received and Herman Levin, who directed 'My Fair Lady,' saw a typescript of the book, liked it, and tried to get a studio interested. He approached six major companies, but they were owned by conglomerates and afraid of doing a political film.

"Rights were finally bought by two young men, Leonard Goldberg and Robert Sterling. They raised money by selling limited shares in the production, leased facilities from Metro Goldwyn Mayer, and then they ran out of money after spending $4.5 million, with only 11 shooting days left."

The producers were finally persuaded to declare bankruptcy, but the film got into distribution, and will open on May 18.

Condon's work shows the special resonances between fiction and the public subconscious, but he is skeptical about its impact: "Anyone who buys a novel and reads it for information is crazy. I don't think any work of fiction, in film or book, has ever changed anything - including the works of Harriet Beecher Stowe."

But he says, "If you can make your points allegorically rather than factually, you can give them more impact and staying power. If only 2 percent of the millions who will see the picture become skeptical about the statements of people like kindly Dr. Kissinger, we will be way ahead."

Then he slips back into pessimism: "I have this recurring nightmare in which, by some series of flukes, John Connally becomes president of the United States. If that happens, Richard Nixon will be our secretary of state."

Meanwhile in Ireland, he is working on his new novel: "I have written 55 pages of 'The Averted Eye' about the Council of Constance. At one time in the Middle Ages, there were three popes. The ruling powers decided it was bad for business and called the council to straighten it out, and all the jugglers and gamblers and prostitures in Europe gathered around to join in the fun.

"It was the beginning of modern power politics and the parallels with Washington D.C. today are remarkable." CAPTION: Pictures 1 and 2, Richard Condon, by James M. Thresher