When you first arrive in Thailand I’d suggest that you drink bottled water all the time. There’s an initial adjustment period of a couple weeks or months where you’re going to get food poisoning or sick from water or something anyway – but, better to have bottled water for first couple months I think.
Later you can drink the water in the pitchers at the inexpensive restaurants you find all over the country. The water is bottled 99% of the time – Thais don’t want to drink their own tap water either. When you get ice – ensure the ice is round, like big, elongated life savers and you’ll probably be safe. That’s also filtered water.
If you’re staying long term you can buy water in 5 gallon jugs for 12 baht, but you must leave a deposit on the jug. You then take it back and replace it with a new jug of water for 12 baht. I think our jug was 60 baht.
Brushing teeth? For first couple weeks I used bottled water and then I’ve used tap ever since. Up to you, probably better to play it safe for a few months with bottled water.
I find Singha water to be the best tasting.
How can you stay safe in Thailand?
You can start by getting Thailand Survival Guide 101.
Thai Black Book.
For a current state of the country – see the ultimate Thailand Guide – Thai Black Book – your guide to staying safe in Thailand
Thai Black Book information site- >