I've been staying in Thailand for approximatively a year, working for a french company. I don't speak any Thai and i can still survive. However, it looks like if you can actually speak Thai, people accept you more and are less reluctant to communicate. Moreover, it brings much more opportunities in terms of work.

Also, i can't exactly see how some people manage to learn Thai by themselves, without a private tutor or a school support.
I study Japanese before and looks like as for Thai, it is important to "crack" the grammar and learn as much vocabulary as possible. Regarding pronunciation, just one solution: talk to Thai as much as you can (same for Japanese), whatever your mistakes are.

So i've decided to join a Thai School.

ps: Thormaturge, nice picture. Bryan Ferry forever.