Thaiss signed a minor-league contract with the Astros on July 24.
Thaiss was cut loose by the Red Sox in mid July, and he was brought in on a minor-league deal shortly after. He then missed a 10-day stretch in August while on the temporarily inactive list, but he returned to the team Tuesday. He's appeared in two games since for Triple-A Sugar Land (0-for-7 with two strikeouts).