[dsaxton]

Villain limps with an A up on 3rd, catches one his best cards, and checks into a trashy board? Unless this guy is incredibly cautious and/or clueless, he is betting 4th whenever he has nothing, which is why I usually suspect a slow-play in these situations.

I would just release my hand once he bets. Raising is by far your worst play since the pot is tiny and the benefit of getting him to fold a few outs is and not worth the risk of running into a better hand. There is some chance he calls with a worse hand, but I doubt it when your hand is this obvious.