The 33-year-old Thompson was active for Wednesday night's game against the Boston Red Sox. To make room on the roster, outfielder Brandon Guyer was placed on the 15-day disabled list with a left shoulder strain, and right-hander Jeff Niemann was transferred from the 15- to the 60-day DL.
Thompson has spent 13 seasons in the minor leagues. He has not appeared in the majors since 2004, when he was with the Kansas City Royals for six games. He was batting .307 with no homers and 11 RBIs in 29 games for Triple-A Lehigh Valley this season.
With nine players currently on the DL, the Rays were in the market for a backup center fielder.