My son (18) could be taken for both Thai and falang (white skin, falang nose, his dark eyes are a bit Thai, a bit falang, black hair. He's never had any problems. He speaks both Thai and English fluently, his English teacher has given over the English class to him to teach because his own pronunciation is so abysmal (he once introduced himself to me as "I am a teacher", I understood, I am a tee shirt). He wouldn't look foreign in London or Bangkok.