It's just for an episode focused on Thomas wondering if anyone's ever going to come get him out of the labor camp.
I'd take that; I didn't like how DS9 just left him there with no follow up. Much as I like Will, Thomas was always a much more interesting character.
Peter David did something with him in the novel Imzadi 2.
Canon there are some interesting and boring ways to go. Boring is that as soon as no one is paying attention he dies in an "accident". Or when the new Cardassian civilian government takes over he is released. Interesting things that could be done are Section 31 getting him out to join them. Or when the Cardassians joined the Dominion him getting brainwashed to be a weapon (depends of what the Enterprise was doing back then besides the Baku incident).
Official Pub Crawler #68 "Sorry About Your Damn Luck!"