He previously visited the Oakland Raiders.
Thomas has torn his anterior cruciate ligament twice in recent seasons, but returned last season to start seven of 16 games played.
He recorded 67 tackles, one sack, one forced fumble and one interception.
For his career, Thomas has 298 tackles, 12 interceptions and seven sacks.
He's a former second-round draft pick from USC.
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Aaron Wilson covers the Ravens for The Baltimore Sun