Strangely enough, I find myself agreeing to a large extent with Butterfly on this topic. I have learned some basic Thai in the time I have been here, but since I live in the city, speak English with the wife and English is my working language, I rarely have the opportunity (or need, more likely) to speak Thai. In fact, when I started in this job (Thai company), my boss told me that her staff needed to learn better English, and that she wanted them to get more exposure to the language!
I guess I could spend a few hours a week to learn the Thai, but even if I did learn to speak and write/read with ease, what use would it be? There is very little Thai literature to speak of, the TV is, as far as I can tell, absolute rubbish, and the great majority of Thais I come across in my daily life speak English rather well, and could probably not be bothered to converse in pidgin Thai, anyway.
My kids are gradually becoming trilingual, and I am picking up a bit of Thai from them(!), but if I was actually going to take time off to study a language, I would either have a go at improving my German or Bahasa, or learn a useful and widely used language like Spanish, Arabic or Mandarin.
There is another aspect of this debate as well - as long as foreigners (and I am talking urbanites here, you guys out in the sticks don't really have a choice!) learn Thai, we are removing one reason for the locals to learn English. I have been teaching our live-in nanny to speak some basic English, basically for the kids sake, but it could certainly give her the option of working for a foreign family in the future, should we decide to move to another country.
To those of you who have mastered Thai, I salute you - well done. But please accept that some of us have little incentive to do so, and quite frankly - very little need for it.
Would life be a little easier if I spoke better Thai? - probably. Do I think it is worth the effort? - probably not. I'd much rather play with my kids, hang out with friends (including a few Thais!), travel, play, work in my garden, read a good book or watch a good movie, or cross swords with the TD intelligentsia!