Maybe it's the cologne?
All jokes aside, I have never experienced anything like the OP describes. Quite the opposite, I find Thais very open and welcoming, and always up for a laugh or a joke. Not to say that they drive me mental sometimes.
However, on entering bars, restaurants and song-taows, I am often in the position of having to be very selective of where I sit because of the look/dress/demeanour of some Europeans.