He then joined the Toronto stage company of Second City, moving on, after three months, to become a regular character on "The David Steinberg Show". Returning to Second City, him and other cast members, including former cast from the Chicago group, created Second City Television (SCTV) for the Ontario-based Global TV Network. The program began airing in the 1976-77 season and won Thomas an ACTRA Award for his work on the show as Best Performer in a Variety Series. He has received critical acclaim and popular appeal for his impression of such personalities as Bob Hope, Walter Cronkite, Liberace and Elton John.
Thomas has written several screenplays, including "High Finance" for Paramount Pictures and the adaptation of the book, "Runestruck" for Columbia. In 1979, he co-wrote the screenplays for "Never Say Mountie" and "Spys like us" with Dan Aykroyd. Thomas and five other cast members of SCTV starred in a one-hour pilot, "From Cleveland," for CBS. He also had a role in the feature film, "Stripes", with Bill Murray and has appeared in the CBS-TV productions of "Rimshot" and "Riel". In 1980, the year Rick Moranis (Bob McKenzie) joined SCTV, the show moved production 2500 miles west to Edmonton Alberta, Canada. For the NBC-TV Network version of SCTV, Thomas was honoured with an Emmy Award for comedy writing.
After SCTV, Thomas worked in both television and film, including a role on "Grace Under Fire". He currently lives in Los Angelas and has his own production company, "Maple Palms Productions".