Wow, why are you so concerned about this? You seem to be very self-conscious about the fact that you are dark skinned, which is totally unnecessary. I get that you might have had bad experiences with some douchebags, but that's their problem and not yours. No one should be experience fear of being judged or discriminated because of the color of the skin, and this includes you. You let "them" win, if you don't feel good about right? Remember this. And here's a fact: people in Thailand won't care if your white, black, yellow or even green. Okay, green would be odd, but I suppose it'd be all the same. Be a nice person, relax and smile, and I bet the Thais will surprise you because you've never seen so many genuinely smiling faces.