it happens sometimes that when you send a message to a new person and they see that you are from what they call a third-world country (which is not true about Thailand. it is so developed and nice now. even the skytrain in BKK looks better than Ukrainian subway trains) they think you want to ask them for money :(
sometimes people get letters from Africa and crooks try to steal their credit card number...
I think that's the main reason, not because they hate asian people
and yes, you shouldn't think about it too much
just let it go
talk to people you like
:)