Thomas, whose father was of Welsh descent, came from an extremely musical family. After studying psychology at the University of Nebraska however, he worked as a school guidance counsellor before entering Stanford University to study for a master’s degree in child psychology. On learning that the University’s opera department was to mount a production of Falstaff he auditioned and was cast as Fenton. This experience formed his decision to train as a singer; and having studied for three years with Stanford’s professor of singing Otto Schulmann (who had worked as a répétiteur for Karajan at Ulm before World War II) he made his operatic stage debut as the Haushofmeister / Der Rosenkavalier with the San Francisco Opera in 1957, later also s...