It’s a variation of this style of rural Khmer house:

That’s a beautiful house. I love that they just said fuck it and let the rain spout spray into the cistern from 5 feet off the ground

look closer. I think it has one of those rolling out type drain sleaves, that will roll out when it fills and then roll back when its empty

upon further review, you are right, it looks like a s-trap on the end

Looks like a blue s-bend at the end. Would create a gross spot for mosquitoes to grow.

Are they built in flood-prone areas, or are they just on stilts for fun?

Gotta watch out for those un-walled houses though, I knew somebody who got one once… thing looked just like a gazebo.

Walled house

Are there houses that aren't?

Beautiful design

Cool. Friends of mine and their toddler daughter lived in a small Cambodian village for about a year about 30ish years ago. They said after about a month or two of living there the village got together and got them a front door as a welcome gift because up until that point they didn't have one.

I can’t answer for these houses but in northern Australia, where it is incredibly hot and humid, they (used to) build houses like this to improve airflow and help keep the house cooler, as well as for flood protection.

In Lismore (also Australia), the stilts had to be high because white man built a town where the aboriginals warned it floods routinely. Guess what we found out in 2022? Turns out no matter how tall the stilts are, you'll still get flooded.

I guess if you’re a hobbit

There sure are, especially prevalent in Cambodia

Is the photo of something else? The image clearly shows a building with walls.

No the photo is correct. They’re two story structures where only the upper floor has any type of wall, and the word wall there is doing a lot of heavy lifting. They aren’t really part of the structure of the house, and can often be detached or opened. Depending on the style of roof they don’t even go all the way up to meet it. The unwalled ground floor isn’t “underneath” the house like one of those stilted New Jersey shore houses, that’s actual living space.

This is opposed to the type of house in OPs post or in the western world where the entire structure is enclosed by permanent walls.