While I haven't spent a huge amount of time in Chiang Mai I realized that as well. I think, sadly, that the reason for the absence of massive amounts of stray dogs in your city is not because of better levels of responsibility, but the military presence in that city would make culling something that would happen a lot more frequently. I've been told by people that work in an animal rescue up there that the shirts people put on the dogs are also indicators that the dog is looked after and fed to some degree and this is a sign to the people that would do the culling, to not do so to this animal, because it is "owned" to some degree. Strange.