my Google plus circle, I stumbled upon the account of the borough (Chumchon) Tha Ruea (ชุมชนตลาดท่าเรือ) of Surat Thani city. Though still an inactive account, it is the first of the municipal subdivisions which I found in Google plus. But when I looked for some more information about the boroughs of Surat Thani - the city website sadly has no such list, so it a bit more searching was necessary - I next found the facebook page of this borough, which is much more active than their Google plus. The header artwork of their page then to my surprise did not show the emblem of the city, but an emblem specific to the borough.
So far, to my knowledge it is only those administrative units to have an emblem which are also a legal person - thus the provinces, the municipalities and TAO, the PAO (which however usually share the same artwork as the province) and Bangkok and its district. The other districts however have no emblem, since they are also no legal person. I have never before seen any borough emblem, and also don't know whether the borough have legal person status or not, but since this emblem looks very much like the other official emblems there may be even more emblems of administrative units than the nearly 8000 of the types listed above. Its a pity there seems to be no heraldic books on Thailand except those few published by the Department Of Fine Arts.
emblem of Tha Ruea depicts a Chinese style ship, which fits the name and location of this borough - Tha Ruea means "harbor", and it is located directly at the river front harbor of the city. Though harbor is a bit of an exaggeration, there are only very few ships there - and to me it always seemed like they are permanently moored there, as I never seen any ship leave or noticed them change position.
Anyway, now I am of course curious if the other 42 boroughs of Surat Thani also have such emblems, or if the boroughs of other municipalities have such artwork as well. It is really sad that in most municipality websites, there boroughs are either not mentioned at all, or just as the list of their names, but no detailed information.