"The In-Laws" should get a death grip on the funny bone of movie goers reduced to helpless mirth by "Blazing Saddles," "The Silver Streak" or "Foul Play," three painfully facetious unfavorites of mine.

The fact, "The In-Laws" unites the original writer of "Blazing Saddles," Andrew Bergman, with the director of "The Silver Streak," Arthur Hiller, for a heavy-handed, smugly cynical farce that might well be called "Foul Play '79."

Alan Arkin is a respectable, nondescript New York dentist whose placid life is disrupted when his daughter becomes engaged to the son of Peter Falk, a government agent involved an apparently harebrained and criminal scheme to steal and sell engraving plates for U.S. currency. The in-laws meet for the first time at a party at the Long Island home of Arkin and his wife, Nancy Dussault. Falk, behaving oddly, excuses himself to make a long-distance call from the basement.

While nosing around, Falk hides some stolen plates in a handy vent. The discovery of this loot the next day precipitates further complications that force Arkin (for no urgent reason, even in the ocntext of material presuming to be screwball) into allowing himself to be manipulated by Falk.

One idiotic thing leads to another, and Falk drags Arkin off on a chartered flight to an apocryphal banana republic. In an episode that briefly lowered my high resistance, the apparent owner of the plane - James Hong as a Mr. Bing Wong - cheerfully instructs a bewildered Arkin in the standard safety procedures. Arkin is the only passenger he's speaking to and Mr. Wong speaks in Chinese.

In an episode creepily similar to the ambush at Jonestown, the plane lands and the dizzy gringos are immediately greated by sniper fire. But the resistance rises back up there as Arkin and Falk go through elaborately unfunny maneuvers to dodge bullets. Arkin, fiendishly witty, ad libs the following howler to a make-believe corpse: you're dead, right?"

Falk's devious shenanigans are resolved to the screenwriter's satisfaction with the appearance of Richard Libertini as a silly South American tyrant. Among other symptons he does an impression of Senor Wences and has a Z-shaped scar on his cheek.

A do-or-die yockfest, "The In-Laws" relies on the willingness of spectators to play along with whatever gag occurs to the filmmakers at a give moment. Bergman doesn't score enough winners to make one anxious to play on his side, and Hiller's style is strictly sloppy-boppy. Far from transcending the material, Falk and Arkin look coarsened and diminished by it.

Hiller's amazing lack of resourcefulness is apparent in a sequence in which Falk and Arkin are on the freeway trying to lose bad hombres tailing them in another car.

If Hiller is at a loss for business, Bergman seems indifferent to any code of comic logic or emotional integrity. At the start we're supposed to sympathize with Arkin, a presumably sane man caughe up in a lunatic's machinations. Although there's never sufficient cause for Arkin to assist Falk, one recognizes the tradition in which a rational protagonist is swept up in wacky circumstances.

What can't be tolerated is the hypocrisy of the denouement, in which crazyman Falk is suddenly revealed as a smart cookie after all, so much so that the once bedeviled Arkin goes along with his sceme to split a few spare million overlooked by the Treasury Department. Originally sympathetic because he distrusted the loony, the nice guy is supposed to endear himself at the fadeout by becoming as crooked as the loony.

Bergman's obliviousness may be an occupational hazard of wise guys who spend too much time in Hollywood. Watching his characters pat themselves on the back for their greedy cleverness, one gets the unpleasant feeling that Bergman is congratulating himself in advance for making a killing.

I suppose it would be asking too much to expect "The In-Laws" to be about the frequently hilarious behavior of in-laws. Authentic human comedy requires another sort of humorist. CAPTION: Picture, Peter Falk, left, and Alan Arkin