"Ain't Misbehavin' " is causing its delightful mischief again. Ten years after this musical tribute to Thomas "Fats" Waller made its Broadway debut, the show is strutting, scatting and striding its stuff in an anniversary revival that opened recently at Baltimore's Mechanic Theatre and is destined to return to Broadway in August.

Remounting a Broadway musical after only a decade is fairly unusual, but what's extraordinary about this revue is that the original cast is back, beginning with Nell Carter, who won a Tony Award for her performance. Joining her are Armelia McQueen, Charlaine Woodard and Andre De Shields.

Ken Page is rejoining the production shortly; his role is currently being played by Ken Prymus, who was Page's replacement on Broadway. Together this vocal quintet does Fats Waller proud, singing 31 songs either composed or recorded by the late Waller.

One song has been added to the original score, an extra solo for Miss Carter titled, "This is So Nice, It Must Be Illegal." It's a fine addition and it fits right in after "Find Out What They Like," Miss Carter's duet with Miss McQueen in which the two ladies compare strategies for pleasing a man.

* MOVING ON _ Sir Peter Hall, the dazzling, combative director whose plays shaped an era on the British stage, is bidding farewell to three decades of state theater to run his own private company in London's West End.

Never shying from controversy and always insisting on the highest artistic standards, Hall has battled vociferously for government support for the arts. He, Trevor Nunn and Peter Brook have been hailed as the three great directors of post-war British theater.

Variously described as a visionary, a power-mad dictator, a reckless workaholic, charming, ambitious and naive, Hall, 58, has countered criticism and a few flops with a series of critical triumphs and box office smashes.

At the helm of the Royal Shakespeare Company (ABC), which he founded in 1960, Hall brought about a revolution in the speaking of Shakespearean verse, changing it into a chatty, accessible form, even daring to make alterations to the Bard's text.

* HOW MANY WAYS are there to look at immigration? Playwright Joanne Akalaitis has found a great many and written them into "Green Card" as scenes and vignettes.

It's interesting and well played by a versatile cast that keeps switching accents and becoming new characters. But the production doesn't build the way a play with a narrative line does. Impact also is lessened because the evening has an over-all sense of classroom learning about it.

"Green Card," first performed at the Mark Taper Forum in Los Angeles in 1986, is now running at the off-Broadway Joyce Theater. The play is part of the First New York International Festival of the Arts and is the first entry in this summer's American Theater Exchange at the Joyce.