Not sure if it also actually comes from Chinese communities (or maybe it is, I just don't realize it), but here in Indonesia, there's this somewhat widespread belief that if you're eating sambal (Indonesia's very famous chili condiment), the best way to get rid of the spiciness is to wash it down with hot water/tea.
It may or may not work at times, though, so it's definitely a case-by-case wisdom IMO.
I wouldn't be surprised. It's a running joke that whenever we feel sick or uncomfortable in any way, the remedy is to just 'drink more water' (implied warm water).
Having grown up with sambal, I can give a few tips if you want to reduce the pain from spiciness. Sambal's spiciness comes from capsaicin, a compound in chili peppers. Capsaicin can bind with lactose, which prevents it from binding to your tongue, so drinking milk or ingesting some kind if dairy product is an easy solution to the spiciness.
It also helps to have some sort of creamy thing to coat your tongue and reduce how much of it is exposed to the chili. I eat nasi lemak with hard boiled eggs all the time, and the fluffy egg yolks really help with that.
Water (whether it's hot or not) doesn't react with the capsaicin. It might even be worse, since it can agitate the settled capsaicin and make it react with the tongue again, causing more spiciness. At most, it might carry away loose capsaicin so the spiciness won't get worse, but it's not the best at it.