Born in Mart, Texas, Thomas often shadowed his father who was a general practice Doctor. Later, he attended the University of Texas at Austin where he studied chemistry and chemical engineering, graduating with a B.A. in 1941 and an M. A. in 1943. While Thomas was an undergraduate he met his wife, Dorothy (Dottie) Martin while she was training to be Journalist. They had three children. Thomas entered Harvard Medical School in 1943, receiving an M.D. in 1946. Dottie became a lab technician during this time to support the family, and the pair worked closely thereafter. He did his residency at Peter Bent Brigham Hospital before joining 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."