I'm telling the truth, I promise!

Today on the way home from church, we had a taxi driver who was thoroughly confused by my appearance... how could I possibly NOT be Thai? How could I look so Thai and not possibly speak Thai? I kept telling him (in my limited Thai) that I was American, to which he would laugh, look at me in the rear-view mirror, shake his head and mutter, "Hmph...Thai, look same. Hmph... American." They never seem to believe me around here...