HANDSOME, GRAYING, slightly disheveled, monologuist/actor Spalding Gray could be that popular, eccentric, sometimes outrageous college professor whose lectures were always packed.

Gray opened his four-week visit to New Playwrights' Theater with a 90-minute monologue called "Swimming to Cambodia, Part 1," the first of six pieces that will be presented in repertory. He's just a guy sitting at a desk talking -- engaging theater boiled down to its bare essentials.

An evening with Gray has the feel of a late-night, cocaine-fueled, elbows-on-the- table talking jag by a particularly fascinating friend. The performer hurls himself pell-mell into his personal view of history and close encounters with individuals rare and common, using tripping cadences that recall the Beat poets and colossal run-on sentences that might make Faulkner's hand hurt.

"Swimming to Cambodia" is made up of Gray's impressionistic, autobiographical ramblings about his minor role in the film "The Killing Fields." Flipping through a spiral-bound notebook, Gray strikes the pose of a wide-eyed WASP witness to weirdness, a stranger in a strange land with an unerring eye and ear for the bizarre and the bohemian.

It wouldn't be fair to tell his tales here -- most performances of "Cambodia" will vary slightly. ("Cambodia," Parts I and II, runs through Sunday; on Tuesday, Gray moves on to the next segment of the self-revelatory series with the adolescent memories of "Sex & Death to the Age 14.")

In "Cambodia, Part I," Gray free-associates like a poet or novelist, jumping back and forth in time, making connections between thoughts on why we were in Cambodia, how actors act, the unreality of war and the movies (instead of wars, Gray suggests, why don't nations pump the money and energy into making war movies, which are just as cathartic and more therapeutic?), bad situation comedies, ritual superstitions, potent drug visions, lewd life among the pleasure- loving Thais and other plangent tangents.

Several times Gray returns to a particularly frightening theme -- the chilling fact that the personal quirks of one erratic individual can control the body counts.

Some of the stories fly, some fall flat, but Gray succeeds in reconstructing the flotsam of his life into some kind of shape and meaning. He seemed tense and wary on opening night, but this kind of personal work seems to depend on the temperament of the audience and the actor's state of mind.

Like performance artist Laurie Anderson, who also comments on America from a slightly skewed perspective, Gray is adept at using his voice and the microphone for dynamic effects. Leaning over a plain desk, sleeves rolled up, looking like he's ready to armwrestle the audience, Gray beins quietly and builds in intensity and volume, leaning into the mike suddenly and startlingly, altering his Rhode Island-inflected voice subtly for characterizations, and ending each "scene" with an oblique moral and a gulp of water.

At one point Gray says he views himself as a "wandering poetic mendicant," constantly in search of a "perfect moment." When it works, which is more often than not, Gray makes his life his classroom and novel and theater. SPALDING GRAY -- At New Playwrights' Theater through May 12. Here's the schedule: "Swimming to Cambodia, Parts 1 & II," through Sunday; "Sex & Death to the Age 14" and "A Personal History of the American Theater," April 23-28; "Travels Through New England -- Spring '84," April 30-May 5; "Interviewing the Audience," May 7-12. Call 232-4527 for performance times.