Mai Ben Rai
I don't mean this picture to be crude. Rather, I include it because it exemplifies a lot of interesting things.
Note, first off, the hose and squirter by the side of the toilet. Thai people (except for their feet) are very clean. And when they use toilet facilities, they like to have water around to wash their private parts. Actually, most Thai toilets are "squat" toilets, which basically means a hole in the ground with some place to put your feet. There is always water there as well, but typically it's kept in a big barrel with a scoop you can use to pour water on yourself and wash your waste down the hole.
I get the sense that Thais don't feel as though toilet paper really gets you clean. I also get the feeling that many Thais don't like sitting down in the bathroom. Many would rather squat, with only their feet touching places where others have been.
If this sounds unmanageable to you, don't bother travelling to Thailand. Alternatively, stay around fancy hotels for rich folks, particularly foreigners. Don't go out into the countryside.
One other thing this picture exemplifies, that I enjoy, is the Thai spirit of "good enough." Thais are practical people and show attention to detail when it matters.
The thing is that what matters to Thais isn't the same as what matters to most westerners. Building codes, e.g., are much laxer (or nonexistent?) in Thailand, and things tend to develop in a more Darwinian fashion than, e.g., in Europe and the United States. To most Thais a few leaks in a bathroom and a mismatched toilet seat, if they don't impede the actual functioning of the facilities or the safety of the patrons, aren't a big deal, except in the homes of the wealthy, and the aforementioned fancy hotels.
You will often hear the phrase mai ben rai, which can mean anything from "it really doesn't matter" to "you're welcome." You'll also hear the word sanuk, which means "fun." Thais tend to lose interest in things that aren't, on some level, fun. And they usually don't agonize over details that, to them, aren't really all that important.