Michael Thomas was an accomplished British stage and television actor. He appeared in more than 100 plays. At Chichester he was the tough, loyal Kent to David Warner's Lear (2005) and Sebastian, the central character in Rattigan's In Praise of Love (2006). At the Old Vic he played Reverend Parris in Yael Farber's acclaimed revival of The Crucible (2014). At the RSC Michael was Exeter in Ed Hall's Henry V (2000). At the National his roles included the schoolmaster in Pillars of the Community (2005), de Stogumber in Shaw's Saint Joan (2007) and Lafew in All's Well That Ends Well (2009).
As well as Festen (2004), at the Almeida he appeared to critical praise in Waste (2008), directed by Samuel West, and Before the Party (2013), directed by Matthew Dunster. West observed that he was "consistently the best thing in most of the jobs he did". His last performance, in 2018, was a hilarious Sir Anthony Absolute in The Rivals at the Water Mill, Newbury.