Most of Thai are very friendly (I have some very good Thai friends - bot male and female) but once upon a time I had problem with a crazy motorcycle rider. I was walking on the walkside on RamaIX and there was a horrible traffic. One of the riders wanted to omit the jam and rode on a pedestrians place, bad, there was not enough place for us both and he scratched his motorbike. As you can imagine, he stopped, started to yell on me, even spit, he wanted me to pay for the scratches (funny guy - rode on the pedestrian area and had some problems). It was not more than 1 min, there were some security guys, 2 minutes police arrived. No problems for me, big problems for him. Really, you can feel almost 100% safe in BKK.