There Is No Such Thing as an Empty Bottle in Thailand
Bottled water is 7 to 15 baht, ice comes in two different kinds with different rules, and the single question that identifies the safe one is written on the sign in Thai nobody can read.
At a street stall the ice arrives in two plastic tubs. One has ice that has clearly been scooped out with a metal cup all morning. The other has hollow tubes of ice, each with a hole bored through the middle, floating in water. Nobody is wearing gloves and nobody looks worried. One of these is the reason a large fraction of travellers have had a bad week, and it is not the one most people assume.
Last verified 5 September 2026.
Tap water
Bangkok's municipal tap water is treated and is technically potable, and the water pressure is high. It is not what you drink. It has a distinct taste from chlorine and old pipes, and the practical risk is not the water but the pipes, which are old in places and are not maintained to a standard you would want to bet a fortnight of your trip on.
Outside Bangkok and the big cities, the quality varies considerably and the rule that holds everywhere in Thailand is the same and is not negotiable: drink bottled water, and use tap water for brushing your teeth, showering, and washing.
Bottled water costs 7 to 15 baht for a small bottle. It is available at 7-Eleven, at every restaurant, at every stall, and in bulk at the shop near your accommodation. It is the cheapest thing you buy all trip and it is the thing that will save your trip.
Refill stations exist in the tourist areas where you exchange a large bottle for a small one, which is what locals use and costs a fraction of the price. They are cleaner than they look because the water is filtered in bulk and the shop has a business reason not to poison anybody.
The two kinds of ice, and the rule
"Straight ice", Thai: nak gang sai, meaning front ice, is ice cut from the front block. It is a solid block chopped with a cleaver into cubes, and the cleaver and the block are the same ice the whole time. This is made from potable water. This is the ice you want.
"Bottom ice", Thai: nak gang lang, is ice shaved off a block sitting in a water bath. It looks softer and frostier, and it is the one in the street tubs. It is not safe.
The distinction matters because the bottom-ice tub is the one sitting in a street cart in the sun, and the cart may have no running water, and a person scooping from it with a bare hand is a genuine risk. None of that is a criticism of the vendor, who is running a business in a country where this is how ice is made everywhere, and the people eating it are not customers, they are family.
The sign that tells you, and nobody can read it
Stalls that care put up a sign in Thai, usually red and white, that says which tub is which. The safe one is labelled nak gang sai.
You do not need to read Thai for this. Learn the one phrase, or simply ask, pointing at the tub: sai? means "can I have this one". A thumbs-up and a pointing gesture is sufficient and works everywhere.
And a very practical rule: if the ice is in a metal cup or a tub sitting in meltwater outdoors, do not drink it. A clear bag of ice with a hole in each piece, in a sealed plastic bag, at a place that looks like it has a business, is almost always the straight kind.
Other things that are not what you expect
Restaurants, even small ones, almost universally use proper straight ice, because a restaurant has a reputation to keep and a stall does not. If you are eating at a proper restaurant, this whole question does not arise.
Street stalls vary enormously. A busy stall in a good location with a queue has an incentive to be careful. A quiet one at 2am has a different set of economics.
Bottled water seals are the check. If the seal on a bottle is broken, or the cap is not original, or the bottle has been opened and re-closed, do not drink it. This happens in tourist areas.
Ice in a hotel minibar is fine. Nobody is sourcing that from a street cart.
Brushing your teeth
Using tap water to brush your teeth is generally considered acceptable in Bangkok and the major cities, and this is the one place the "bottled water only" rule is relaxed, because you are not ingesting it and the risk is low.
Where the local water is genuinely questionable, use bottled. The cost is 10 baht and the peace of mind is worth it in a place you have chosen partly because the water is uncertain.
What actually gives people diarrhoea
It is nearly always ice or salad, not water. Raw vegetables washed in tap water, and ice from the wrong tub, are the two culprits.
Peeled fruit, hot food, and food that has been sitting cooking hot are all safe. Street food cooked in front of you at 90 degrees is a different proposition from a salad sitting in a bowl of water.
And the best precaution is not paranoia, it is timing. In the first two days your stomach is unprepared. Be careful in the first forty-eight hours and be relaxed after that, because the risk profile genuinely changes and so does your tolerance.
Bottled water, straight ice, and a thumbs-up gesture at a tub. Three things, a few baht a day, and the single largest reduction in avoidable misery available to anyone travelling in Thailand.
