IN "GOOD MORNING VIETNAM," Robin Williams dazzles you with his rapid-fire performance as a fast-talking Saigon deejay in the Armed Forces Network. How much you enjoy the war story Barry Levinson weaves around Williams' funny warps depends on how much you can ignore it.

Levinson elicits amusing performances from his characters (actors J. T. Walsh, Bruno Kirby and Forest Whitaker; with Cu Ba Nguyen as Jimmy Wah, a smiling bar owner with Las Vegas demeanor), as the director of "Diner" and "Tin Men" again makes you feel his gift for male-to-male banter. But how much Levinson directed the improvisatory Williams is open to question. Probably not much.

Levinson proves a buck private when it comes to war settings: The endless footage of jungles, palm trees and Vietnamese villagers is little more than a slide show of Thailand (where "Vietnam" was shot). When you're not watching cinematographer Peter Sova's aerial views, you're fighting nausea from his tightly framed shots of Williams as deejay Adrian Cronauer in his radio booth.

Mitch Markowitz's script isn't sure whether to make the war a visual backdrop or an integral part of the story. True to Hollywood instinct, it opts for both. Sometimes the characters resemble the lightly drawn incidental folk of the TV series "M*A*S*H" -- including local kid Tuan (Tung Thanh Tran), or his attractive sister Trinh (Chintara Sukapatana), whom Cronauer falls for. Then suddenly, there's a last-minute story about a Viet Cong spy who stakes out GI hangouts added to the footage of soldiers getting shot and various Vietnamese Are People Too scenes.

The screenplay takes the studio tour approach: "On your left is the Romantic Moment, where Cronauer meets local gal Trinh. But he doesn't sleep with her because we in Hollywood respect all cultures, not to mention trends. And hey! There goes the Conflict -- Sgt. Major Dickerson (Walsh) and Lt. Hauk (Kirby) are jealous as military Salieris about Cronauer's talents. And ma'am, please don't drop that candy wrapper there -- we're passing through the Local Color Section's swaying palms, street scenes and jungle paths . . ."

"Vietnam" actually works best as the "M*A*S*H"-like passion play, with Walsh as a hawk who can't stand anyone having fun in a war zone and Kirby as a prig who resents Cronauer because of his own secret comic ambitions.

"Vietnam" will do well on the strength of Williams' performance: He's Groucho in 'Nam, with his rapid-fire quips and cast of imaginary guests, like the fey clothes designer who advises troops to avoid camouflage -- "Make a statement. If you're going to fight, clash." Cronauer's also teaching an English class (yes, there's a war on but this was the only way to meet his love interest), teaching them New York insults.

When he tells his students he's from Queens, one asks, "What are Queens?"

"Tall, thin men who like show tunes," he replies.

But when it's time to mourn Cronauer's departure, after a final softball game with the locals and a farewell to buddies-in-arms, there isn't a wet eye in the house.

GOOD MORNING VIETNAM (R) --

At area theaters.