It's a bitch to clean though compared to tiles.
But if you have a maid then that's her issue. Anyway I've been pondering this issue myself: Where to put the bathroom in a Thai style wooden structure in such a way that it doesn't end up as a brick & cement eyesore disrupting the overall look of the wooden structure. Having it outside is one option, having it in the middle under the house (instead of on a side) is another, or even on the first floor on the side but somehow avoiding bricks and tiles.
There are practical concerns though; outdoors in lush greenery sure sounds nice, but the reality of it all would likely be dodging snakes, centipedes and mosquitos at 4am when going for a pee.
So I'm leaning towards having it on the upper level, but avoiding bricks & tiles as much as possible, and have it as open as possible while probably still under the/a roof structure of the house