His first screen appearance was in an uncredited role in the 1950 B-feature film, I Shot Billy the Kid, with lead Don "Red" Barry.
Keymas was cast in ethnic, often Native American characters, or cow-punching, at times ruthless, cowboys, in countless film and TV Westerns.
He portrayed "the Leader" in The Twilight Zone episode "Eye of the Beholder", which originally aired November 11, 1960.
His freakish, ambiguous character was seen throughout the episode on a futuristic big-screen monitor as background subplot to the story.
In 1962, he played a murderer in "The Nancy Davis Story" on the TV Western Wagon Train.