Where: AUA on Ratchadamri, 5 min walk from Ratchadamri BTS.
Hours/Week: For me, 25-30 hours per week but it is completely flexible. There are classes every hour from 7am to 8pm M-Th, 7am to 5pm F, and 9am to 4pm Sat. Closed Sun. You can go any hours you want.
Cost: 102 baht/hour for Level 1 (-3 for every level you move up), 12% off if you buy 200 hours at a time, plus 50 free hours if you attend 200 hours in 8 weeks. I've been getting every one of these discounts and so it's been only around 70/hour.
11 months ago before I came to BKK, I literally didn't know a word of Thai. After studying just 9 months at AUA (granted at 25+ hours/week), I can converse fluently (though speaking at an advanced, near-native level is still a VERY long way away).
The AUA method is fully immersive. You just listen, and listen, and listen, and this teaches you not only to understand but also to speak. It is incredibly fun and works wonders if you are willing to put in the time. I would never want to learn another language using any other method. Read the "Attempting to Learn Thai" posts in my blog if you want to know more.
www.daninbangkok.blogspot.com