Joe has something but that is more like a sidecar on the bike to pick up broken down bikes. Not sure if he will rent it out though. Maybe Phil can ask as I am in Laos at the moment. Can also try the Norwegian guy (sorry can't recall his name at the moment) with his monster trike but again he loves his "baby" very much so I doubt very much if he would rent it out.
Otherwise it may be difficult as trikes are not really legal in Thailand. There is a guy who makes trikes on request but these are normally small bikes like step through Honda, etc. I think Ally posted some time ago a picture of his shop with the phone number.