Note everyone is used to having chlorinated and flouride(d) water so their bodies might have been used to relatively dirty water. Of course, I could wrong in their case...don't know their background
Here is an article from Cambodia, where they are some years behind: https://medium.com/make-a-difference/bringing-clean-water-to...
Thanks for the inside info. But do they brush their teeth with bottled water? Do they wash their dishes, tomatoes with bottled water or with "dirty" tap water?
Sarcasm aside, I'm sure it varies from place to place, but in places I've been to in Thailand (and I live half there, half EU), tap water is fine for washing/brushing and if anything, too chlorinated (and thus not too drinkable). I still drink bottled water (or filtered water; many local friends have filters installed to their tap).