You are basing your assumption that, "I hear the girls in Thailand don't use lube, which is probably a good reason why their HIV rates are high" on HIV rates for a different continent which has totally different social and economic values to Thailand and a snippet you read from somebody on a Thailand discussion forum.
Undoubtedly HIV is a problem in Thailand as it is in most parts of the world but to say HIV transmission in Thailand is higher than anywhere else is pure speculation. As for the lube, well just think about it.