Airside there is a massage place, I think it is near pier 3 (gates 31-36)? It is easy to spot; it is housed in a model of a traditional Thai wooden house. I am not sure what the opening hours are? When I walked by it recently ~ 05:00 it was closed but there were many people sleeping in the comfortable reclining chairs used for massages. I think I remember a few posts about complimentary massages in one if the TG lounges but I have never seen this first-hand.