Ummmm, Thailand is probably one of the only countries in the world that somewhat unoficially recognize thress three -- men, women, ladyboys (kayoeys).
Don't worry about it. Just be yourself, have fun, and trust me, especially in the gay scenes of Pattaya and the likes, you won't have any issue. Just don't get aggressive and/or defensive, let your guard down, and have a good time.
Really, nobody is going to give two shits that your trans. I guess you might run into some drunk Russian on the street or something, but in the gay areas? No worries...