"It will be very good for me to go back and I hope I will do well there," he told the U's official website.
"There have been times where I think I shouldn't have left, but I think I have also been unfortunate here.
"I was feeling fit when I arrived but I haven't had much time to play so I am very happy to go back to Hamilton and play some football."
Thomas should go straight into the Hamilton squad which hosts Celtic on Saturday.
Source: Team Talk