I think a lot has to do with the particular officer you get on the day, and of course if he happens to be in a good mood today. I think generally a police officer will decide if he likes you or not within the first few minutes of an encounter and it's probably based on superficial or silly things - if he likes the way you dress, or the colour of your bike, maybe he likes or dislikes people with beards/tattos, or you happen to support a football team that he likes...
Of course, as I have said before, if you go around with the attitude that "All police [or even Thais in general...] are our to get you" then that will come out in the way you act to the police and you will probably change the mood of the officer so that things go against you (and the guy behind you probably; so thanks for that!
But I remember one time I was stopped by an officer who had pulled me over many times before. I was just about to show him my licence when he waved me on and said ok ok (as he'd seen it before). Just as I was about to head off a more stern looking police officer came and started looking at my tax disc and giving my bike the once over for potential violations. The original officer, who it seemed had taken a likening to me, said in a chirpy voice "no this one is fine. He has a Thai licence. Thai girlfriend too". The more stern officer just grunted and let me go on my way.