@shinjin977: I have to strongly disagree about not going to the south of Thailand. I spent about 2 weeks on the isles of koh samui, koh pangan and koh tao and I never felt safer. It certainly felt safer than Bangkok. Of course you should stay safe but it's not like it's dangerous just to be there.
Also, I had the best food of my 2 month trip around Vietnam and Thailand on those isles.
You went to 3 tourist trap island. ("Koh" in thai means island) and yes south of thailand is some crazy shit. It is on multiple country's dangerous to travel list and when I was 6, riding in my dad's car going down there on business, I saw 2 guys in get a fender bender and it ended with one guy shooting another guy right in the face (no punches were throw before hand btw). My dad told me to get down and we quickly drove away. This is not some crazy story btw, shit like that happen more than thai police like to admit. The sex slave market/capital of the world is also located down there. Just recently a British couple were brutally raped and murdered. Not saying bad things will adsolutely happen but like I said before, 2 hours south of bangkok shit gets risky and bangkok is no haven. The lesson here is be very careful travelling anywhere and for the love of god DO NOT GO TO ISOLATED PLACES.
Another good tip is, do what the locals do, in Thailand for example, good honest people considered going out to night clubs/drinking places to be kind of shady. Why is that? Because asian night clubs and bars are fucking shady as oppose to the western world where people go to chill and that is considered normal. You will see local people drinking in local favorite restaurant on the side of the road instead. Have fun, asia is a blast and do not trust people coming up to you to tell you about bars/hotel/tourist locations. At best those are terribly expensive tourist traps, at worst those are actual financial/physical/sex traps.
Oh I almost forgot and this is VERY important, when in Thailand DO NOT speak badly or preferably don't speak at all about the royal family. because of le majeste law, you can go to jail for the rest of your life if you drunkenly joke about doing the queen or something.