Thomas was born in India. When he was six years old, he moved to South Africa. He moved again to England in 1967, where he has written, directed and produced 40 major documentaries and dramas, including Death of a Princess (1980).
Monday, 14 June 2010, saw the public release date of the documentary film For Neda, made by Thomas with the help of Saeed Kamali Dehghan, on the death of Iranian demonstrator Neda Agha-Soltan. Kamali Dehghan secretly filmed Neda's family and obtained footage of her life and death for the HBO documentary.