Welcome to the forum.
But WOW! All those HIV tests??? This was an essentially zero risk exposure. It is unlikely your partner had HIV, since few Thai sex workers are infected. (Thailand has had one of the world's most effective HIV prevention campaigns among sex workers, and things are much safer than 10-15 years ago.) Second, with condom-protected vaginal and oral sex, the chance of transmission was virtually zero even if your partner had HIV.
Most important, all your tests after the combo test at 4 weeks were superfluous. The combo test (antibody plus p24 antigen) is 100% reliable at 4 weeks. Your subsequent results were unnecessary but confirmed that you didn't catch HIV. To your specific questions:
1) Yes, these tests are pretty much the same world wide. And as you know, Thailand is a medically sophisticated country with diagnostic test standards not materially different than in Europe or North America.
2) HIV test results always overrule symptoms. Yours are not typical for HIV, but even if they were, your test results prove HIV isn't the cause.
3) See above: 100%.
4) For sure you don't need any more testing. You can forget this sexual exposure and go on with your life with no worry about it.
Best wishes-- HHH, MD