No idea about the parts, but if you are going to Thailand, make sure you stop off in Phuket for a bit of R&R with all the extras thrown in.
The south western area has some picturesque beaches. The central western area has everything you could want. The north western area has a more isolated; less tourist orientated feel to it.
If that's not you cup of tea, then hire a scooter and try to keep up with the Thai scooter taxis - those guys are suicidal and will have you dripping with sweat; the sweat you only get when facing fear; the fear of real and impending death at every turn - """i love it"""; in fact it's so good that i'm going back to Phuket for my third year in a row.