Whereas most of the municipalities have just a handful of boroughs (Chumchon, ชุมชน), when I had a look at the website of Ubon Ratchathani recently I was surprised to find that there are quite a lot of boroughs in that city. On their map subpage, it has a map and list of 106 boroughs, and even detail maps for (almost) all of them. As the city has a population of about 85,000, this means each of the boroughs has about 800 citizen. Sadly I cannot find a table with the data for each borough, only other information piece is area which is written into each of the details map, e.g. for Chumchon 106 named Wat Burapha 2 (วัดบูรพา 2) the value is 1,436,513.09. The unit is missing, but as the whole city covers 29.04 km² it seems this is square metre and not square wa (ตารางวา).
While I already knew that Chiang Mai has a similar number of borough - 90 split between four subdistricts - the number exceeding 100 poses an interesting problem for the geocodes of the boroughs. Though they are hardly found, and I haven't yet found any complete list of these codes, it seems that they follow the system of the administrative villages (Muban) by using the last two digits of the 8 digit code. Thus the first borough Ban Kan Lueang School 2 (โรงเรียนบ้านก้านเหลือง 2) would have the code 34990001, and the last allowed code would be the 99 for Wat Si Pradu 1 (วัดศรีประดู่ 1). The final 7 borough however have no space in this system anymore.
It would only fit in case there is another level of subdivision in between - the two zeros could be used in case there are Khwaeng in Ubon Ratchathani same as in Chiang Mai, and though I have found nothing which would prove any like this the map on the Thai Wikipedia shows four areas with distinct colors. Even if these aren't official city subdivisions, using such would allow to fit in all the codes. Another possible escape would of course to use something inspired hexadecimal notation, after 99 continue with A0. The least preferred escape would be to use the last four digits for the boroughs and give borough 106 the code 34990106, as that would break the hierarchical structure of the codes.