He was born on March 15, 1920 in Mart, Texas. His father was a general practice doctor and often shadowed him. In 1941, Thomas earned his B.A. and studied chemistry and chemical engineering at the University of Texas at Austin. He also earned his M. A. from there in 1943. Thomas met his wife, Dorothy (Dottie) Martin while he was an undergraduate. He had three children with her. In 1943, he went to Harvard Medical School. Thomas worked closely with his wife after she became a lab technician during this time to support their family. He did residency at Peter Bent Brigham Hospital before he joined the US Army. "In 1955, he was appointed physician in chief at the Mary Imogene Bassett Hospital, now Bassett Medical Center, in Cooperstown, N.Y., an affiliate of Columbia University."