last year when I was in Bangkok, I became friends with a gogo boy from "Boys Bangkok"
I think he was taken with me or just thought I was good tip material... But anyway..... He was more than happy to tell me who the best numbers were at each bar.
He told me the dancers that had the biggest cock and the ones are give the best fuck.
Most times he said to get there early and off them because they are in high demand.
I am not a size queen so I only listened and smiled.
So.... I would suggest you find a gogo boy that has been around the block a few times and is willing to share some info