[gargamel]

If your route takes you through southeastern Thailand, I'd plan to spend a few nights in a beachside bungalow on Koh Chang for somewhere around $30 per night. There isn't a lot of culture there, but there are some cool warerfalls to see, it's peaceful during the day, and the shisha bar on White Sand Beach is fun at night. (edit: I see it took me too long to type this on the iPhone and Hemi-Cuda beat me to it, but now you have 2 recommendations for Koh Chang)

My main advice for Bangkok is to eat as much street food as possible, ignore the guide book, and go to whatever hole in the wall restaurants have the longest lines of locals. That's true everywhere, but due to the amount of tourists in Bangkok, your chances of getting a bad meal there are relatively high if you don't choose wisely. Also, the city has earned its reputation for hedonism, but you wont really notice the sex industry unless you go looking for it. Having said that, Soi Cowboy (featured in The Hangover 2) may be worth a quick stroll at night just for the spectacle of it.