Thomas attended University of California, Los Angeles, where he was a history major and played for the UCLA Bruins football team from 1998 to 2001.
Following his 2000 junior season, he was named UCLA's Defensive Most Valuable Player and was a second-team All-Pac-10 selection after leading the team with 88 tackles (nine for losses) and six forced fumbles.
As a senior in 2001, Thomas led the Bruins with 111 tackles (26 for a loss) and had 6.5 sacks, forced two fumbles and defensed five passes.
St. Louis traded Thomas to the Green Bay Packers at the end of training camp on September 4, 2005, for cornerback Chris Johnson.
He started 10 games for the Raiders in 2007 but appeared in just two in 2008 before suffering a season-ending hamstring injury against the Atlanta Falcons on November 2, 2008.