We ,being foreigners here stick out as a sore thumb.
This means we get looked at and graded(judged) by the way we look and act.
Our looks are what they are,how we act we can control.
I have been here for a little while now and sometimes i also get treated with disdain.Mostly only just one person.
The rest is fine and there for my day is good.
I always try to be nice and respectful and in a full bus i will call people out and invite them to sit beside me.
That works!
Speak a little bit of Thai and smile a lot,it works!
Where i live most people know me and i feel i am treated like just another
person by them.
OP,you seem to be too sensitive and care too much how you are perceived by others.
Try the lite approach,relax and stop worrying.