I can assure you that it has nothing to do with your "white face"- I have ethnic Thai friends who can testify to that.
Have you ever come across dual pricing ? ie one price for the locals and another for the farangs. Visit Madam Tussauds or Siam Ocean World in the Siam Paragon shopping center and white faces are charged more.
I have made countless trips to Thailand over the past twenty years and am aware of many of the local scams tried out on tourists, ranging from the jet ski scam (pay $$$ for damage you caused whilst hiring it) to the "free" shows at the upstairs bars in Patpong.
The scammers in Thailand are without doubt the smarmiest con artists you will ever run into. So why do I keep returning ? Beautiful country, amazing food, 5* at 2* prices. I'll be going back in a couple of weeks when I'll be:
Getting dental work done at 1/3 of Western prices.
Having clothes made to measure at a similar discount.
New glasses made at 2/3 of home cost.
Staying in a resort town with daily spend on accommodation and food of about the price of a decent lunch for two in Paris.
As an experienced visitor I know I might be charged a bit extra than a local on one or two things but I'm not going to end up with a rip off bar bill or find I've brought a lady boy back to my hotel by mistake.
Anyone going for a visit needs to Google "Thai scams" beforehand and keep their wits about them at all times.