That brings back memories. We went to Thailand to play rugby back when I was in college and I remember going to the bars with they guys and you had to remember this word (that I've forgotten since) to ask the girls and it means "Ladyboy" because some of them were fine as hell and you seriously CANNOT tell.
Sure some are obvious with the hands, face, adams apple etc...but there are some that are fine as hell when you are sober so you can imagine how many dudes can get fooled if they had several drinks in them and shit.
best part of that trip = eat like a KING for $20 a day. Seriously, crab, steaks, whole chickens for $1..it was sweet.