Thomas said that he decided he wanted to become an actor at age eight, after watching a PBS special on acting and realizing he had found his calling.
After landing a part at an open audition in a San Antonio, Texas, hotel, Thomas made his film debut in Raggedy Man (1981). At age nine, Thomas auditioned for the lead role in E.T. the Extra-Terrestrial (1982). He won the part by giving a genuinely tearful performance, during which he drew upon his real-life trauma of having seen his pet dog being killed by a neighbor’s dog. The film’s success exceeded expectations, and Thomas was troubled by the sometimes extreme reaction of the public.
Thomas returned to Texas and starred in Cloak & Dagger, while attending school. He returned to film in the late 1980s and early 1990s and began to prove himself in adult roles, most notably as the younger version of Anthony Perkins’ Norman Bates character in Psycho IV: The Beginning. Thomas dropped out of Texas’s Blinn College (where he studied philosophy and history) after one year to act full-time.
His most prominent adult role to date was as Samuel Ludlow in Legends of the Fall (1994). He played Johnny Sirocco in Martin Scorsese’s historical fiction film Gangs of New York (2002). He is currently both an actor and musician and starred in the 2011 film The Last Ride (2011) as musician Hank Williams Sr. In the ABC series Betrayal, he plays T.J. Karsten. He also played Tom, the father of Carla Gugino’s character, in the 2017 Netflix original movie Gerald’s Game.