Area theaters playing "Guyana: Cult of the Damned," risk a drastic decline in the sales of soft drinks in paper cups at the old candy counter. They also risk turning civilized audiences into disgruntled mobs, since the Guyana tragedy has barely been illustrated, much less dramatized, in this miserably minimal production.

"The Story Is True. The Names Have Been Changed," say the credits, and so Rev. Jim Jones becomes Rev. Jim Johnson, Jonestown is called Johnsontown, and the late Rep. Leo J. Ryan (D-Calif.) becomes Rep. Lee O'Brien. By the time the cyanide cocktails are trotted out, however, no one could possibly care about anything but the location of the nearest exit.

The idea of a quick, cheap movie about Guyana is abhorrent but hardly unprecedented in the history of motion picture exploitation. More unsettling is the fact that the filmmakers have managed to depict the communal suicides of 900 people in such a clumsy, feckless way that the tragedy becomes completely unaffecting.

Thus the movie does not really pose a problem for the faint of heart. In fact it is really a film for the faint of head.

As the demented reverend, Stuart Whitman barks and stalks through the movie without an instant's repose; usually he is shouting lunacies into a hand mike, working the crowd like Phil Donahue or a Las Vegas comic. Among other once-respected performers drawn into this act of self-abuse are Joseph Cotten as a lawyer and Yvonne De Carlo in the quintessentially thankless role of Johnson's press agent.

The years have not been all that unkind to Yvonne De Carlo but Twinkies and Tasty Cakes have. There now appear to be two of her living in the same body.

The narrative, more fits than starts, is held together with the adenoidal narration of a cult member never identified as a character on the screen. He details the deterioration of the sect, although in the film it starts as a cross between the Bund and the Symbionese Liberation Army anyway.

In an early scene, Johnson is addressing a churchful of followers in a manner reminiscent of Prof. Irwin Corey, and the director seems determined to get a reaction shot of every single face in the crowd. The technique, if it can be called that, turns into a motif and quickly into a stalling tactic.

Once in Guyana, we even get reaction shots of two big-billed birdies sitting in a tree. When the town is founded, they are seen sitting on a branch. When Johnson metes out garish tortures to three little boys, they are seen sitting on the branch. And when everybody drops dead, there's one more shot of Heckl and Jekyll, apparently still trying to size it all up. o

Oddly enough, details of life at the camp and of Jones' modus operandi have been toned down from published news reports. The infinite variety of his sexual appetites, for instances, has now become quite finite.The film doesn't even have the courage of its own sleaze; in fact we are beyond tastelessness here, and beneath it. We're into the realm of anti-taste.

The producer, director and co-writer of the film is Rene Cardona Jr., who made "Survival," a similarly slovenly item about cannibalism among plane crash survivors. His future productions include "Boat People" and "Kill the Shah." Cardona doesn't just keep his finger on the pulse; he sinks his fangs into it.

Universal, which acquired "Guyana" for release, is owned by MCA Inc., a company that is now a $1 billion-a-year operation. Surely the additional couple mill to be brought in by this abominabl cheat could be done without. It is hard to imagine gains more ill-gotten.