No, do not drink the tap water in Thailand. You will most likely end up with food poisoning, even if you’re in a nice hotel or resort.
Stick to bottled water throughout your trip. Ice is usually made from purified water, so you should be fine. But if you’re concerned, just ask for no ice when ordering drinks.
If you are eating street food and they offer water out of a cooler, decline and get bottled water nearby.
When you brush your teeth, use bottled water.
When in the shower, do NOT rinse your mouth out with the shower water.
Be safe, not sorry!
