TV news reports that the water pipe carrying drinking water into Bangkok has damage and water may be contaminated. They say, check the colour, smell, look for any signs of contamination before using it. Bottle water is sold out, I've been using boiled tap water.
Now I think is a good time to remember what we did on the farm before clean drinking water. Obviously we boiled drinking water too, but that often wasn't good enough, since solid matter would still make the water dirty. We used a crystal, that you would swirl in the water, to clean it first. See aluminium sulfate.
These crystals are sold on the streets of Thailand (usually in small hardware/general stores, the kind that sell buckets), they are for water cleaning. Take some dirty water, swirl the crystal in the water and you'll notice the dirt clumps together. Heavy clumps fall to the bottom, and sometimes lighter scum floats to the top.
In the video below you can already see the dirt sticking together almost immediately. After 20 minutes, the water is practically clear except for the pile of dirt at the bottom. A pretty dramatic transformation.
Once the water is clean of contaminants, boil it to kill any bacteria and you have water fit to drink. If you can't boil the water, then you can use sulfur powder, shown in block form above, sold in the same place as the crystals. Mix this into water and it will kill bugs and bacteria.
Another option is the SODIS method, or walk down the street to Starbucks, this is Thailand after all! Not a third world country, you're never far from a supply of clean water here.
These crystals are also used to scrub under the arm pits to remove small hairs and eliminate odor and to sooth the face after shaving for men.