i had no choice but to learn. i was stuck in a little village in isaan, broke, and there was not a sole within a 30km radius who spoke english.
i bought english/thai phrasebooks, set aside an hour per day, and did one page per day, revising the previous page each day and marking the phrases i had had difficulty with, then kept going back to them 'till i had them off pat, crossing them off as i got them right. two phrasebooks later, i was walking around making a **** of myself, speaking thai to everybody. they would correct me and eventualy i started getting the hang of it.
you reach a stage where everything starts falling into place, and then you progress very fast.
the grammar is very simple and easy, but you have to remember that almost every word has up to five different meanings, depending on the accent or tone placed on it. i found that if i ignored the bloody tones, concentrated on vocabulary, then spent a lot of time listening to people, trying it out, and forcing myself to watch thai tv, i could get the gist of a conversation, then got to the point where i could do business, or at least make myself understood.
i don't think i will ever get the tones completely right, but i have one hell of a vocab. and get by to the point where the locals come to me for translations, etc.
you just have to keep at it, and discipline yourself.
good luck