I'll give you one word on the BKK ladyboy scene - caution. First off, I've never been with a ladyboy in Thailand, so my info should be taken with that grain of salt. Been around them plenty, but never taken a test drive, that I know of (the post op's can be near impossible to spot). I travel to Thailand twice a year to visit friends, and know the country fairly well. One word of advice that friends who live there always give first time visitors who visit the bar areas is "be careful of the ladyboys." Of course some of that has to do with them passing themselves off as girls and the guy, who is not looking for 'something different', getting a rude surprise back in the room. But it goes beyond that in the safety area. Ladyboys in BKK are famous for theft, sometimes ending in violence when they work as groups. The ones who do this are in the minority, but it happens enough to be wary of. Never, and I mean never slow down and even talk to the "girls" along shadows of the main drag (no pun intended), Sukhumvit Road, late after the bars have closed. More often than not, these tend to be the hardened ladyboys who can't get a job in one of the clubs. You have a better than even shot at finding your wallet missing.
In BKK, a decent place to start is at Nana Plaza, a wildly popular night spot made up of countless bars, all filled with ladies for hire. It is located on Soi 4 and Sukhumvit, a block or so from the J.W. Marriott. Many bars will have one or two working, but on the second and third floor are a couple or three bars that are filled up with nothing but ladyboys. They tend to be a tad more agressive than the girlie bars, as you can be walking by and some of the ladyboys will try good naturedly to pull you inside. As with the girls, if one is gonna take someone for the night it is always better to take one from the bars because if something does happen, or something turns up missing, you have a better shot at some relief. But never have anything to do with the girls/ladyboys along the street. There are some places in the Patpong entertainment area, but I usually stick to Soi Cowboy and Nana so sorry but I can't give you any info on that.
In Pattaya they have a couple of famous places with female impersonators, and I'd assume that would be a good place to start. Again, sorry but no first hand knowledge but you could easily find that out down there. By the way, Pattaya is about an hour and a half taxi ride from BKK ($25 or so, up to $50 if you book through your hotel). Just find a taxi driver you like and cut a deal. If you need any rec's on places to stay that have good locations, are safe and for good prices, send me a note. Also have a good source for air tickets that is much better than going through the airlines. One note on airlines - if you are going from anywhere in the Eastern part of the U.S., you'd do well to try to fly Northwestern through Detroit. The connections can cut up to 20 hours off your trip - each way! When you're old like me, the extra hours take a toll. Hope this helps.
