Korea and Japan are not poor countries, girls willing to work there can make a lot of money off the local men. And they are both pretty racist, and traditionally the cultures of both countries have not been very open to foreigners. I've heard numerous rumors that local men really look down on girls that go with foreigners, and won't see them again.
Thailand has a culture that has always been much more open to and accomidating to foreigners. And it's poor, a girl working in a bar that'll stay with you all night for a price that most would think is very cheap can take home a comparative fortune to her village back in the Northeast (where the "big" money is in rubber trees, i.e. latex, yes, they grew up surrounded by condom trees).
Phillipines has similar levels of poverty. And a history of Spanish and American colonization and rule, whether they like white people of not, many previous generations were ruled by them. They don't see them as dirty outsiders that are beneath them.
So, can't speak for the OP, but I'd certainly be happy to enjoy some Koreans and Japanese with my Thai, but due to price, selection and availability, I stick with cheap and easy, and never bother with the extra effort.
