Two of Britain's top theater directors have sued the Sunday Times of London for libel over an article alleging they reaped huge profits from commercial exploitation of plays they originated at state-subsidized theaters.

In a June 29 article, the Sunday Times said Sir Peter Hall, director of the National Theatre of Great Britain, and Trevor Nunn, codirector of the Royal Shakespeare Company, had made millions from plays like "Amadeus" and "Les Miserables" while their theaters had gotten much less.

Hall, at the center of controversy last month when his theater's adaptation of George Orwell's "Animal Farm" was dropped from the Theatre of Nations festival in Baltimore, said the article was a "perversion of truth," a "deliberate and willful distortion" and "a piece of character assassination on both of us."

The newspaper said Hall had made $3 million as director of Peter Shaffer's "Amadeus," while the National, where the play originated, had received only $750,000.

"Wrong," Hall said. "I earned 720,000 pounds more than $1 million from the commercial exploitation of 'Amadeus' over a period of four years or so. The National has earned 1.2 million pounds about $1.8 million , and the money is still coming in."

Nunn, who is directing "Porgy and Bess" for the Glyndeborne Opera and whose other extracurricular work includes the hits "Cats," "Starlight Express" and "Chess," issued a statement calling the article "dreadfully inaccurate and scurrilously defamatory." 'Ma Rainey' Author to Visit

August Wilson will be in town July 27 to see the Studio Theatre's production of his play, "Ma Rainey's Black Bottom." This is the first production since the play ended its acclaimed Broadway run last year.

Wilson spent last weekend at the National Playwrights Conference in New London, Conn., where he watched a staged reading of his new work, "The Piano Lesson" -- the fourth in his series of plays, each set in a different decade, about black Americans after the abolition of slavery. Wilson's "Fences" is scheduled for a Broadway opening next spring. Building a Mountain

Producers of "Shout Up a Morning," the La Jolla Playhouse production that comes to Washington in exchange for American National Theatre's "Ajax," had to cancel two of last week's preview performances due to "technical difficulties," according to a Kennedy Center spokeswoman. Specifically, workers needed more time to weld together an 1,800-pound mountain that travels across the stage on a railroad track. The musical, based on the legend of John Henry, features a score by jazz artists Nat and Cannonball Adderley and opens tonight at the Eisenhower Theater. Coming Attractions

"Legends!," a comedy starring Mary Martin and Carol Channing, comes to the National Theatre Aug. 12 for a three-week engagement . . . The Flying Karamazov Brothers will perform their new show "Juggle and Hide" at Arena's Kreeger Theater Sept. 2-21. Theatre Festival Offerings

This week's offerings at the sixth annual Washington Theatre Festival include Romanian playwright George Astalos' "Our Daily Tea," which runs tonight through Thursday at Source's Main Stage. Nick Mathwick's "Waiting for Marge," winner of the 1986 D.C. Commission on the Arts and Humanities Larry Neal Award, opens Saturday at the Main Stage. For ticket information, call 462-1073. Odds and Ends

"Hooray for Yiddish Theatre in America!" -- an exhibition featuring posters, playbills, costumes, memorabilia and a film celebrating the heyday of Yiddish stage and screen in the United States -- has been extended at the B'nai B'rith Klutznick Museum through August . . . Harold Pinter's "Betrayal" begins a four-week run tonight at the Olney Theatre . . . "Beehive," a revue of the music of the great women singers of the '60s, opens tomorrow at Arena's Kreeger Theater . . . The Amazing Kreskin performs his mental stunts tomorrow through Sunday at Petrucci's Main Street Dinner Theatre in Laurel . . . The Source Theatre Alley marks its debut tomorrow with "Women Behind Bars," which runs in the outdoor theater through Aug. 2 . . . "Voices Burning: Visions of Home," a showcase of multidisciplinary performance work by Washington area women artists, will be presented Thursday through Sunday at the Sanctuary Theatre . . . Theatre Banlieue, a Belgian experimental theater troupe, performs "Eclaboussure" Thursday through July 26 at the Jarry.