I just realized that a very handy tag would be to extend the toilet tag so that one knows what the cleaning options are. Off the top of my head the options can be:
none - for no water
shower - for hand held ones
combined - for integrated japanese style
bucket - self explanatory
IMHO, the “integrated Japanese style” might as well be toilets:wash=washlet tag, per Wikipedia.
Again, Wikipedia suggests bidet (saved everyone a click: taps with a small sink) is slightly different than the usual bidet shower. I guess fancier toilet amenities might offer these kind of bidets (with sinks) rather than the usual bidet showers.
But then again, toilets:wash=shower gets the job done. For those special ones, might be toilets:wash=bidet.
Buckets? I reckon cistern (toilets:wash=cistern) might better fit the description for something like this. In short:
toilets:wash=cistern (with a water container)
toilets:wash=shower (the usual, ordinary cleaning option)
Clarifying: I use the tag toilets:handwashing=yes/no to indicate a sink with faucet(s) where one can wash hands but I assume you’re talking about the spray hose for, in Wikipedia’s words, “genital and anal cleansing”, right?
I don’t believe those small spray attachments found in most Thai toilets should be tagged the same as an actual bidet. It’s not a big deal to me either way.
You might gain some insights into a tagging scheme on the Tagging mailing list. (You might also end up with many opposing viewpoints and no clear conclusion.)