They do that because in Thailand north east girls are not seen as beautiful. It might be racism. And many girls are running from there past.
When they have found a farange they might ask for surgery from you .
I will therefor just tell some foreigner to think about this when they meet a woman from North East Thailand.
I use only this as an example how many Thai woman today make themself "new". And if you married a Thai woman from North Est you will hear she want have this done also.