Well first ever post, thought best to get it out the way.
Been to Thailand many times, went a lot of times over xmas through to new year - saving up holiday from work and going for a 4 week period at a time. Got a few friends who ended up living there. Can even speak Thai to a degree. Unfortunately have not been since 2010 - but planning to go next year
I would say one of the most fun places to go with a few mates, even gone on my own when started working for myself and had a gap between work.
Had some fun in both Pattaya, phucket, and Bangkok, plus travelled to many other parts of the country. People are friendly and always smiling. General rule would be if you look for trouble you'll find it, but this is a rare occurrence. You can easily meet people to chat to whilst out.
Bada Bing Go Go is meant to be good in Bangkok, Soi cowboy, and narna plaza also. Patpong is ok, but lots of people trying to get you to see some form of show - don't bother. As for Pattaya it's crazy best ask people when your over there and like one of the previous poster said get out about 9:30 to 10 as that's the time the elite get in the GoGo bars.
Golden rule never pick the first one that pays you attention, always have a good luck around.
If you need any more info just pm me