Thomas Baptiste was born in Guyana and came to the UK in the late 1940s. He originally trained as an opera singer, winning competitive scholarships at the Royal Academy of Music and Drama and at the National School of Opera. He also came third in the Richard Tauber International Competition. He later joined Joan Littlewood's Theatre Workshop. Baptiste was a founder member of the Actors Equity Advistory Committee, which campaigned on behalf of black actors in Britain.

According to a transcript in the V&A archive, Thomas Baptiste also played the Duke of Ephesus in Comedy of Errors at the Liverpool Playhouse, date unknown.