If it makes anyone feel any better, my white ass has frequently been complemented on my excellent English… for a Quebecer 
Uh, people, I suspect that Excalibre is kidding.
Okay, this isn’t Thai, but still, it might help. Assuming these ignorant fucks are capable of using the internet, if they ever come back to your restaurant, just scrawl this URL on their check: http://www.bigbadchinesemama.com/home.html
They won’t bother you again. 
In a weird way, it does.
Thank you everyone for understanding. It’s really annoying when you feel outraged, but you also feel like no one gets where you’re coming from or how you’re feeling. I’m glad I can always rely on the Dope for sympathies and some similar and funny anecdotes.
Well if I may, as someone who started working in restaurants about 30 years ago, and has worked off and on in restaurants over the years to earn some extra cash, this is what you do with ignorant customers: First, think to yourself, “I am not the public’s bitch.” Then realize that yes, if you want good tips, there’s an aspect of entertaining the customer. Doesn’t mean you have to stand there and do the cha-cha. Think of yourself as an aspiring actor. Make up a really fake life story. Your ignorant customers want to know why you look Thai but speak English “so well?” Tell them the story about how you were a little orphaned refuge child adopted by American peace workers, or better still, adopted by an American GI who’d killed your entire village but took pity on you and you were raised on an American military base by your father’s GI buddies and then your father was killed in action and the GI’s raised you anyway until your father’s relatives were able to send for you and now you’re working as a waitress because your father always wanted you to grow up and be a lawyer and you’re just working to pay for law school to honor your adopted American father’s wishes, blah, blah, blah.
Do this with a completely straight face.
Some ignorant ass wants personal info on you? Give 'em “the story.” You’ll get huge tips.
You owe absolutely nothing to inappropriately nosey customers, but as a server, you do kinda have to make them feel good, even if they are ignorant asses.
Telling your customers a ridiculous story will help relieve those hours and hours of boring tedium, and provide you with lots of funny anecdotes to tell your friends for years afterwards.
Here on the Dope, it’s our job to fight ignorance. As a food server, it’s not your job to fight ignorance.
I say we establish an ad hoc committee to determine the truth!