Yea the girls and lady boys there have no need to trick anyone, all you gotta do is ask, I wouldn't grab for cock personally as you can just flat out ask if they are 100% lady, they don't get offended or try and hide it. The guys who don't ask are the ones who are closet gays who want to have a cock in their mouth but not come off as being flaming gay in front of their "bros". It's still gay no matter what anyone says.
Have you been on an imaginary trip there then? I just ask as you seem to be generally clueless about the hole thing.
Let me just say this one more time - you don't need to ask. Ladyboys are in one place, girlies in another place. If you ask a regular girl if she's a ladyboy, you'll more than likely get a punch in the face off her. Imagine a chick asking you if you were 100% male

It's a scene. Of course there will be people on their first trip that accidentally walk into a ladyboy bar but if they think that is the case, they'll tell you straight up. I know this because I've taken newbies in there in the hope they'll take one home. Sadly the dicklettes always tell the newb there's going to be 2 cocks in the bed.
It's not an easy mistake to make - their voices rather give it away plus if you walk into a place like that, for sure there will be one or 2 convincing ones and then another 50 that look like Bob the Builder. If that doesn't do it -go to the toilet and see these 'women' lined up at the urinals.
Seriously - if you make a mistake in Thailand - you meant to.