There is that, but Japan definitely has potable water (as does Korea, Singapore, maybe Hong Kong). Also SE Asian countries don't bother with hot water as much as northeastern ones, but they generally don't have potable water regardless.

The airport in Beijing has a hot water dispenser but I've never seen anyone use it.

Hong Kong had plenty of drinking fountains in parks etc, usually with a sign showing it had been recently inspected for hygiene.

The parks in Shenzhen have water fountains too, including low-level taps for pet bowls (so it doesn't splash on them and scare them)

You have to go pretty far down the development scale of nations before you get to undrinkable tap water.

I didn't have any problems drinking the tap water in Bangkok for a week, for example.

I've spent time in Bangkok for several weeks now, and although it seems like it is safe to drink, I've talked to a lot of locals that are buying bottled water too.

Also, the smell of chlorine, when you turn the tap on, is enough for me not wanting to try it.

that's not true. There are only a few countries in south-east asia with drinkable tap water: brunei, hong kong, japan, singapore, and south korea. You should probably not have drunk that water in Bangkok.

Even within a country, whether a specific city has potable water or not can vary. Bangkok technically has potable water from its source, but the pipes it might travel through can be broken and dirty (the same is true in Beijing, actually). In this case, you can get lucky...but it is better not to chance it.

Tap Water is not drinkable in beijing. I used to live there.