Hello,
In most of the world doing hydroponics with tap water is fine, but this being Thailand... I gotta ask... is Thai tap water (hua hin, bo fai area) OK for growing vegetables?
I was taking water from a machine (the one that you put in 1 baht coins) for a while, for my dog, and leaving it in transparent jug in front of the house. After 3 days or so, there was brown sediment (i would guess, rust), and the water generally was brownish, greenish color after 3 days.
So it would seem that the best option is tap water, but not sure.
Thanks.