Tim Conway is one of the most original and inventive funnymen of his generation. His genius for physical comedy - frequently slow-motion slap-stick - and for spontaneous, deadpan verbal wit has flourished in skits on "The Carol Burnett Show" and appearances on talk shows or ceremonial telecasts like the Emmy Awards and People's Choice Awards.

He also seems to be attracted to the movies, but judging from "The Billion Dollar Hobo," an amateurish attempt at a comedy starring vehicle, he's in desperate need of a suitable format and astute collaborators.

Conway has turned up in several Disney comedies, contributing a funny bit here and there but never emerging in a prominent comic role. The inexplicable thing about "Hobo," now at a dozen area theaters, is that it does less for Conway than those Disney outings, in which he wasn't supposed to be the lead. In addition to being wasted as a comic resource, Conway ends up playing second fiddle to a German Shepherd named Bo.

"Hobo" is the first production of an indenpendent company called International Picture Show, which makes its corporate headquarters at the Omni in Atlanta and evidently hopes to make an impression on the family-juvenile film market dominated by Disney.

The company has already completed a second picture with Conway, a dreadful prospect given the sluggish nature of the initial venture. It seems almost certain that they've made a sequel that repeats or compounds the errors and inanities of the original.

Conway is cast as a would-be adorable stupe named Vernon Praiseworthy who can't do anything proficiently. Following a poorly staged introduction in which he makes a shambles of a job as a short-order cook, Vernon is revealed to be the sole surviving relative of an eccentric transportation magnate played by the late Will Geer.

Vernon is promised a respectable future if he can prove his resourcefulness in the way the founder himself did two generations earlier - by riding the rails. Since Vernon's helplessness is pathetically apparent, the admirable Bo is sent along to get him out of scrapes.

Although the script is slowed to a crawl by stodgy, superfluous exposition, there is only one scrape to speak of. Vernon falls in with a gang of dognappers. By the time the film grinds to a fadeout, the premise remains barely developed. At this rate it will take about a dozen movies to get Vernon and Bo to the end of their railroad trip. Maybe the producers can afford a series of comedies as petrifying as "Hobo," but it's not certain Conway can. More to the point, he shouldn't have to.

Hasn't Conway keen around long enough to deserve a more appreciative and professional caliber of support? Stuart E. McGowan, the party credited with the writing and direction of "Hobo," appears to have no flair for comedy. More often than not the camera is rooted in place - and it's rarely a witty or expressive place.

In addition to inert visualizotion, that movie suffers from a sheer lack of comic situations. Conway is allowed perhaps two opportunities to develop a slapstick routine, and neither is sustained. McGowan shows more consideration for the deadly plot, which happens to be the most expendable aspect of the entertainment.

If he hopes to thrive as a movie comic, Conway must work in a looser format with snappier company behind the cameras. He should also take a few pains to counteract the bland dumbbell personality that he's stuck with in "Hobo." Perhaps it would help if he played multiple roles.

And why not?

It would give him the opporunity to experiment with the gallery of characters he's already invented, especially his abstracted codgers and foreigners. If he persists in impersonating nothing except a bewildered naif, he is doomed to cinematic dullness.