What would be a good girl for me would be 1) one I can communicate with (so she should speak a bit of English and me speak a bit of thai at least) so we can know each other and share together and 2) one that we both feel good together and want both to stay together.
I think that the hi class, midle class or poorer class question doesn't change anything ; if you are both well together it doesn't matter does it ? More a question of being able to discuss and exchange about our differences (culture, background, way of life etc) and accept each other and be happy together.
I don't really believe in internet meeting sites. Lots of scams there but also because I believe in meeting in real. The few first minutes can say a lot about each other for me. Mutual attraction and feeling well together just to talk then is very important for me.
I understand also the post about Philipean women prefered to thai women by some. Catholic, use to the idea of living elsewhere in the world as many philipeans do, etc... Can help to get both closer to each other in the first place and can help avoid some difficulties perhaps in some cases. But well, I have visited Thailand twice already and really like the bit of their culture I have discovered and thai people. So I will stick to Thailand for now
As for the classification : good girls / nice girls / party girls / "bad" girls... hum... don't think it is that simple... as some said, a good girl can't turn "bad" and a one time "bad" girl can come out good. Depend on what you are looking for in the relationship and how you treat each other (yep, goes both ways

) no ?
The overall difficulty stay in the "be able to communicate" and "understand the other one ways of life". Impossible to feel good with someone for me if you can't communicate and understand the other well (language and culture). So, no other choice than to learn Thai as much as I can and spend times there (3 to 4 weeks perhaps some time to time) to live and understand better thai culture. Perhaps I will never meet a girl that I like and who like me in Thailand, but I will be happy for the life experience. Might even think about retirement there when time comes, who knows
