RHODES STANDS UP FOR SITCOM.

``Am I showing off too much?'' Tom Rhodes asks, his eyes widening in mild self-mockery.

Maybe. But why not? No one wants a comedian to be a shrinking violet, quivering with doubt or modesty. Though Rhodes' boy-next-door-turned-dropout looks convey an unthreatening sweetness, he's also imbued with a challengingly healthy sense of self.

The stand-up comedian is surprised to find that self playing sitcom. He's the star of ``Mr. Rhodes,'' the NBC Monday night half hour about the foibles of being a prep school teacher.

``I was never a fan of sitcom,'' Rhodes admits as he takes a lunch break during rehearsals for an episode of the show. ``To me, stand-up was the greatest. My hero was Richard Pryor, who, like all the best artists, was the voice of the voiceless, the sound of one man taking on the world,'' says the 29-year-old star.

Rhodes, who grew up in Oviedo, Fla., was about 12 when he first tasted the thrill of live stand-up comedy, watching an uncle perform an act at an open-mike night.

Two weeks after he turned 18, he headed off to pursue a full-time career in stand-up. He experienced a couple of ``horrific'' years in the sticks, traveling by Greyhound bus, performing green material full of references to high school, romance and life on the road.

``At that stage of experience, any joke you can write you use, and as a comedian you can only draw on your own experience,'' he said.

At 21, he moved into the cities - first New York and a couple of years later San Francisco - where he began gaining a reputation. It was during this time that he first tested his skill on television with appearances on Fox's ``Comic Strip Live,'' and A&E's ``Caroline's Comedy Hour.'' Rhodes really made his mark through Comedy Central on ``Two Drink Minimum'' and then ``Viva Vietnam,'' his own series.

It was at the Montreal Comedy Festival, last year, that NBC discovered him and offered him the opportunity to develop his own show. He met with numerous writers whose suggestions ranged from the idea of him playing a Malibu gynecologist to the ``Did You Feel It?'' concept of portraying a seismologist. Eventually he teamed with executive producers Jennifer Heath, Mark Brazill and Peter Noah, who created the teaching concept for him.

``Teaching was the only other thing I could actually visualize myself doing'' says Rhodes, who dubs teaching ``a pretty noble thing.''

``It's definitely a transition,'' he says of his move into the sitcom format. ``Other than wanting to be Steve McQueen, I never wanted to be an actor. I only know how to be myself. I think that's why comedians get their own shows. Comedians spend all their time formulating their own opinion, formulating their own voice, formulating their own persona. That makes for such a strong personality. ... It seems an obvious thing to give these people their own shows.''

However, Rhodes thinks that at first he was rigid and stiff, adopting what he calls ``a gunfighter pose'': back stiff, ready to pounce, with hands curled against the side of his thighs. But he feels he's loosening up and is finding that the laughter (a sound to which he is addicted) registers ``twentyfold'' when he hits the joke right.

``Of course not every joke can bring the house down, but I think on the average we're doing well and being pretty tasteful,'' he says. Rhodes hopes that the show won't go for cheap, sexual innuendo but will try to incorporate some real sense of what a teacher should be amid its laughs.

Rhodes is appreciative of his good fortune, but worries some that it ``might be a drag being a star.''

``I didn't want to be a star. I wanted to be a comedian, meandering into town, moving from place to place like a gunfighter righting wrongs - dispensing justice like a `High Plains Drifter,' then moving on.''

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Photo

Photo: Farrah Forke plays a guidance counselor to Tom Rhodes' prep school teacher in the NBC Monday night ``Mr. Rhodes'' series.