My wife's family friend took me to these weird slums along an (abandoned?) railroad track, different world than the rest of Bangkok. It looked very shady but people were (as usual here) very friendly. The only thing they wouldn't let me shoot was a bunch of people gambling, money changing hands. Then at one point I went ahead to shoot something and when I turned around, my 'guide' was gone ..... I countinued shooting, and after a couple of minutes he re-appeared. We kept walking, shooting, no problem at all.
While driving back home I told him we should go back there tomorrow, but he said it wouldn't be such a good idea, because he was pulled aside by the slum boss, who asked him what we were doing there, why I was shooting. Apparently the slum is all gang controlled. So showing up there two days in a row would make some people very nervous.