Although your question has a lot of detail, the reply is brief: There is nothing in your story that makes me suspicious of syphilis or any other STD. None of your symptoms suggests STD -- most are consistent with genitally focused anxiety. If indeed you had prostatitis, it is unrelated to your sexual adventure in Thailand; prostatitis is not sexually transmitted. But I'm sort of skeptical about that diagnosis anyway.
I think it is time to just forget the whole episode, secure in the knowledge that you have no STD and nothing else connected to the exposure in Thailand, except for the possibility of anxiety over the event as a potential cause of some symptoms. In any case, clearly you have nothing that could ever harm your health or that of any future sex partner.
I hope this helps. Best wisehs-- HHH, MD
I forgot to mention that I have allways been proned to ingrown hairs on my buttox and my upper legs. I also randomly break out on my back and shoulders from time to time.