Pimsleur is simply the best there is. They have a unique system, where you learn something, then learn something else, and then go back and hit you with the first thing you learned...building from there. Someone else here might be able to explain the method in more scientific terms than I can, but I can say it really does work.
I do think it's important to do this Pimsleur course before Thai For Beginners. TFB is an excellent course, but its a much harder learning curve to start with that one.
I studied TFB by making one copy for each of my cars, another copy for my desktop computer, and yet another for the laptop. Also ripped a copy to put on my mp3 player. That works! You can't help but start thinking "bri-sa-nee" instead of "post office".
I've also developed my own method of learned Thai script if you're interested. You can learn multiple symbol-sounds while only memorizing one thing, so its more efficient that simple flashcards. There's memorization involved, just less of it.
Here's how it works. I wish I knew how to do Thai fonts on this board but I dont. Ok, what you do is pick simple words that you can remember. Some words work better than others for this, but lets use the thai word "nana" like Nana Plaza. I like this example because its easy to remember the symbols for the Nana BTS station. The "n" sound looks similar to an English "n" except for the circle-y thing on the lower right, the "ah" sound looks like a cane. If you can remember what "nana" looks like, you've just learned 2 Thai characters and their sounds. Works better with short words like chicken "gai"... So I started out memorizing letters/sounds that way, then made the flashcards to test myself with. The written language looks beautiful to me, so I guess I was motivated. Also the boys are impressed when I can (sometimes) spell their names in Thai:-) It works wonders for making friends.
Dboy