Last season, Thomas had a career-high 55 tackles, one sack and 14 quarterback pressures. He also forced a fumble and knocked down three passes.
In four NFL seasons, all with the Colts, Thomas has 137 tackles, six sacks, forced two fumbles and recovered one.
Colts president Bill Polian has said the team considered this a good free-agency period because they had re-signed safety Bob Sanders, tight end Dallas Clark and guard Ryan Lilja before they could hit the open market.
The Colts have also lost two players in free agency -- starting guard Jake Scott signed with Tennessee and No. 2 tight end Ben Utecht signed with Cincinnati.
Copyright 2008 by The Associated Press