Against all odds and prejudices, Cheech and Chong seem to get better and better. Their new film, now at area theaters, is a vulgar, zany kick.

"Cheech and Chong's Next Movie" decisively confirms the flair for movie comedy that the pair demonstrated so disarmingly in "Up in Smoke." Objectionable as their raunchy sense of humor and simple-minded, potheaded characters may be from a socially responsible standpoint, Cheech and Chong transcend the objections.

They're genuine comic originals whose teamwork comes as a stinging professional rebuke to the rank amateurism of John Belushi and Dan Aykroyd as the Blues Brothers.

Just so there are no misunderstandings, "Next Movie" should be given a wide berth if you find dirty jokes and stoned facetiousness beyond tolerance or redemption. Most of the humor in their rambling scenario derives from the contemplation or pursuit of sexual and chemical euphoria by heroes who dwell in blithe hedonistic squalor and survive by dumb lack or providential grace.

As children as Laurel and Hardy and indestructible as Mr. Magoo, these drug-culture stooges were introduced in "Up in Smoke" as a runaway family man from the Mexican-American district of East Los Angeles (Richard Marin's Cheech) and the hippie black sheep of a prosperous WASP family on the posh side of town (Thomas Chong's Chong). Now a permanent odd couple, living in a condemned house that blights a quiet lower middle-class neighborhood, the boys get by on odd jobs (Cheech drives a van at Universal when the disadventures begin), dealing (Chong reveals that he has sold two lids of dynamite dope to himself) and welfare (Cheech has a girlfriend who's a case worker).

Beer bottles cool in the goldfish tank. T-shirts hang in the refrigerator.

The toilet is inoperative. Ever curious about strange new highs and so far gone that no sensation can ruffle his cheerful, blurry calm. Chong finds a cockroach among his leftover butts, exterminates the unlucky insect and then adds it to an experimental mixture in the bowl of his gigantic pot pipe.

The boys share an enthusiasm for rock music, although Chong, impervious to sounds that deafen everyone else in the neighborhood, Cheech included, tends to get carried away doing Hendrix riffs. One sequence depicts Cheech and Chong collaborating somewhat awkwardly on an ethnic ballad that celelbrates the former's "heritage." According to the most inspired of several tortured verses, "Mexican-Americans love education. They go to night-school classes and all take Spanish and get a Beeeeeeeeeee."

The new movie was directed by Chong, whose on-screen daze obscures an extremely keen sense of timing and an inventive pictorial wit. This too recalls the tradition of Stan Laurel, who played it dumb while directing the best of the Laurel and Hardy films. Chong's precision is quickly evident in a sight gag that finds Cheech, behind the wheel of his car, backing up in order to pitch a line at a gorgeous pedestrian (Shelby Chong, the real-life spouse of his partner). The vehicle backs out of the frame at the right, then suddenly reenters and exits at the left with a patrol car on its tail.

The teams's updated countercultural frame of reference is best suggested by the sequence that incorporates this particular sight gag. Out of gas, Cheech and Chong siphon a few gallons into a garbage can and lug it back to their car. Lacking a funnel, they pour the contents into the gas tank, naturally drenching themselves and the back of the car in the process.

Cheech, slightly more in touch with reality, expresses a few apprehensions about lingering gas fumes when Chong prepares to light one of his monster joints a few minutes later. But, as always, their conversation drifts in other directions, subject to their limited attention spans. Adroitly timed, the delayed-action explosion leaves the interior of the car and the passengers smoldering.

In the wake of Richard Pryor's accident, this characteristic gag has an eerie resonance. But Cheech and Chong are aware of the ominous comic logic behind the behavior of their characters. If left to their own devices, the buffoons would go up in smoke, several times a day. It's only comedy convention that spares them from fatal stupidity.

Cheech and Chong seem more subtle and perceptive than the young dopers who cheer each passing drug reference seem to realize. At the same time, these comics have a knack for overcoming resistance in spectators who feel alienated from or hostile to the drug culture. Numbering myself among the laltter, I've entered both Cheech and Chong movies expecting to be put off and left feeling amused and impressed. The first fresh comedy team attracted to the movies in over a generation, Cheech and Chong appear to be just hip enough in outlook and just traditional enough in style to reconcile extremes.

Even if one tends to recoil from the depraved environment, the clowns themselves remain funny on sight and infectiously good-natured. The mood of playfulness in the midst of hazy L.A. squalor recalls the comic spirit of Henry Miller loose in Paris during the Depression. Like his characters, Cheech and Chong are habitually down-and-out and yet always ready for fun and foreover resilient.

Many of the film's hilarious highlights are as unprintable as Miller's. Among recent movies only Bertrand Blier's "Femmes Fatales" surpasses "Next Movie" as a compendium of blatant, uninhibited, gleeful male sex jokes and fantasies. Generous to a fault, Cheech and Chong retail as many old locker-room nifties as their continuity can accommodate. A lot of ribaldry formerly heard only by men is here for the sampling of women prepared to appreciate its ridiculous effrontery.

Several supporting roles are played by members of an improvisatory comedy group called The Groundlings.A young comic named Michael Winslow does some prodigous mugging and sound effects as a psycho whom Chong inadvertently sits next to and finds merely quaint. However, the most inspired recruit is Edie McClurg, a young comedienne cast as a giddy, cackling matron who turns up in the last half of the film for a night on the town with Chong and Cheech's country cousin, an effervescent hick called Red Mendoza (Marin in a double role, of course). Whenever things get a little slack, the team seems to have enough resourcefulness to bounce back. In a brilliant, sustained fight of silliness, McClurg proves their most impressive secret weapon.

Curiously, both "Next Movie" and "Roadie" end with gags centered around UFOs. Each variation is worth waiting for and seems hilariously appropriate to the comic destinies of the characters. The other family coincidence: These happen to be the funniest new comedies of the season.