Something I haven't found any information about in English are the subdivisions of the municipalities (thesaban). It seems like every municipality is subdivided into entities named chumchon (ชุมชน), which translates to "communities". Big cities have up to 100 of these, while the small thesaban tambon usually only have just one or two. These entities are apparently at a similar level as the villages (muban). Sadly the nearly complete lists of these (and the muban) in excel sheets I found at oncb.go.th are no longer accessible, so there seems to be no online resource listing them anymore. Any information on the tasks, history and so on of these is very welcome.
At least Chiang Mai has another subdivision above the communities - a map at the city website shows four "wards" (khwaeng, แขวง). Oddly the geocode list at DOPA lists only three of the four, but also list a single ward for Nonthaburi. These are probably not the same kind of entity as the subdistricts in Bangkok, which are also named kwaeng. Again I have no ideas on the function of those.