Thomas was born in Gary, Indiana, and began his professional acting career as a Broadway actor, appearing in the 1974 revival production of Love for Love and in the 1975 revival of The Member of the Wedding. Both shows starred actress Glenn Close. Shortly after he moved to Los Angeles to pursue a career as a TV/film actor. In the fall of 1975 he received a role on an episode of The Jeffersons. It was during the taping of the show that he learned of an audition for a sitcom loosely based on the 1975 film Cooley High. Thomas auditioned, won the lead role, and filmed the television pilot, which tested poorly. The concept was quickly reworked into a more light-hearted approach to the source material, and became known as Central Avenue, before settling on the title What's Happening!!. Thomas was the only cast member retained from the pilot, and took the lead role of Roger "Raj" Thomas. The new "summer series" became a ratings hit, and was expanded to a full series, airing from 1976 to 1979.
During the show's run, Thomas was involved in other film and TV projects including Baretta, The Brady Bunch Hour and the film A Piece of the Action starring Sidney Poitier and Bill Cosby. During the first season of What's Happening!!, Thomas was one of the final two actors to be considered for the lead role of Kunta Kinte in the breakthrough miniseries Roots, which eventually went to LeVar Burton. Thomas would go on to play the smaller role of Kailuba in the miniseries.
What's Happening Now!! and later career
After a six-year hiatus from TV and film acting, Ernest resumed his role as Roger "Raj" Thomas in the sequel What's Happening Now!! The show aired in first-run syndication from 1985 to 1988.
