"Die Laughing" certainly dies on the screen, but without leaving much merriment in its decrepit wake.

The most expendable of recent movies, this amateurish diversion for Robby Benson and his presumably undemanding (perhaps nonexistent) public doesn't even justify itself in the amusing, incompetent terms of a traditional clinker like "When Time Ran Out. . . ." which goes out of its way to provide unintentional hilarity.

The moth-eaten scenario of "Die Laughing" was fabricated by Benson, his father Jerry Segall and another collaborator, evidentally under the unhealthy influence of Colin Higgins' "Foul Play." San Francisco is once again the location for a synthetic chase thriller about an innocent bystander, Benson as an aspiring rock musician, who becomes implicated in deadly foreign intrigue.

Benson's group, a placid combo called Rush Hour (Nap Time might be more appropraite), has yet to get that Big Break, Judging from their three vaporous numbers, it's difficult to understand the holdup; the Rush Hour sound must be the quintessence of inoffensive, ineffable mediocrity. The opening song, in which Benson murmurs sweet nostalgic nothings in recollection of his first trip to the barbershop when a mere lad, is particularly numbing.

Until Rush Hour's ship comes in, so to speak, the young leader makes his living driving a cab, recklessly. His troubles begin when he veers across several lanes to pick up a fare who happens to be running for his life. At a stoplight the young hero is too preoccupied with the sound of his own music and babble to notice that his passenger has been killed. A few moments later he does notice someone reach through the window, trying to steal the victim's property, a small case. Eventually catching on, Benson abandons the cab, with victim and murder weapon in the back seat, while clutching the mysterious case.

Now wanted for murder, he endeavors to stay alive, get to the bottom of things and still make auditions (the film achieves its slapstick zenith when Rush Hour goes disguised as five long-bearded Orthodox Jews). All the while, Benson is hunted by the police and sinister types representing shadowy, ruthless interest groups. The object of their nasty interest turns out to be a spider monkey, secluded in the case by its late owner, a nuclear scientist in possession of a secret formula.

Benson's exertions are abetted by Linda Grovenor, a plain reminder of former leading lady Gylnnis O'Connor, as his resourceful girlfriend; Charles Durning as his exasperated but solicitous boss, and Elsa Lanchester as Durning's mother, who evidently took the hero under her wing when he was a street Arab.

The most entertaining presence in themotley show turns out to be Bud Cort, ending a prolonged hiatus from the American screen in the flamboyant role of a demented boy genius, his old specialty from "Harold and Maude" and "Brewster McCloud," of course, but now orchestrated exclusively for villainous scherzos.

Cort's prissily intimidating burlesque of a juvenile Fu Manchu would count for more in witty surroundings -- Brian De Palma's "Phantom of the Paradise," for example. In this context Corts' distinctive nuttiness, which culminates in a creepy impersonation of the late Sid Vicious, provides a few flickers of comic relief and unmistakable style, but it can't rescue an entire film from feeble writing and sloppy direction (by Jeff Werner, a former assistant to that most notorious of movie-making dilettantes, Jon Peters).

Benson still resists trusting his own comic attributes, although his best moments are chipmunky vocal bits and gangly physical bits that recall his amusing resemblances to Jerry Lewis. As usual, he's too protective of a severely limited romantic image -- juvenile pup -- to transcend its soporific limits. One of these days he's bound to be superseded as a junior high school crush (perhaps he has been already by Richard Gere in "American Gigolo" wherever fashion-conscious adolescents congregate). Will he be prepared to compete with John Travolta or merely slip into the deserving obscurity that awaited those moondoggies of the previous generation, Troy Donahue and James Darren?