[erkkie]

I'm a techie from EU and have survived to tell the story of multiple tooth brushings with tap water in Thailand.

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).