http://www.into-asia.com/thai_language/phrases/basics.php lists Thai words for "yes" and "no", and describes other ways of saying yes or no to a question.

http://www.thaifocus.com/phrases.htm also lists Thai words for "yes" and "no", and inter alia mentions a couple of yes/no questions in Thai.

http://www.peacecorp.gov/wws/multimedia/language/transcripts... seems to indicate that Thai even has a special word whose presence in a sentence indicates a yes/no question.

http://thailanguagehut.com/blog/blog/thai-question-words-so-... has many, many examples of yes/no questions in Thai, and shows how to answer them.

What is the basis for your claim that "there are no yes/no questions in Thai"?

(It does seem that binary questions aren't treated the same way in Thai as they are in English -- the conventions for how you say yes and no are different in different cases -- but it doesn't look at all as if there are "no yes/no questions". For that matter, even in English there are some binary questions to which "yes" and "no" would be peculiar answers. For instance, questions that implicitly make an offer ("Would you like one of these?") usually have to be answered more politely.)