Absolutely everyone familiar with Thai culture in the least knows that ALL males are referred to as "boys" --- even if they are 38 years old.    And ALL females are referred to as "girls", similarly.   It is just the terminology they use.    It is a bit disconcerting at first.... to hear them constantly refer to someone older than you as a "boy" or a "girl"....   but you get used to it.    It is a part of their culture and customs.