Also, on the appearance front, having transited BKK a number of times, arriving in a blue blazer with collared shirt and khakis won't hurt. (That's how I travel, the blazer has plenty of pockets.) Also, have reasonable length hair, and make sure that you shave sometime in the few days prior to your arrival. This may all sound petty, but you are looking to play a game to reduce the possibility that you will be stopped in the green channel. All of this stuff adds up to a total package in the eyes of whomever is making the stop/no-stop decision. You want as much on your side as you can get.

Note, I've been stopped exactly once in my life. A few months ago, on arrival at BOS, I was pulled out of line for a thorough search. Eventually, the customs agent and I started chatting, and I finally asked him why he selected me. He said that he works an X hour shift, and is expected to complete Y searches. Therefore, he needs to search someone every (X*60)/Y minutes (37 in my case). I came through at the right clock time. Seriously.