Google helped me to find a collection of some text files containing several geocodes, however only for 14 of the 75 provinces. The thing makes these lists different from the ccaatt list from DOPA - they include the villages (muban) and also the municipalities (thesaban). The strange thing which differs it from the geocodes of the municipalities found previously is the fact they are here listed at subdistrict level, while in the other sources they are at district level. For example the city Surat Thani here has the geocode 840170, while normally it has 8499. I am a bit confused about the municipality geocodes now.
I haven't yet had the time and patience to actually go through the village codes to see if there any oddities, striking differences between the lists I found earlier, but of course I have saved all the files locally to be sure they are not lost if they remove it from the website.
The website is owned by the "Bureau of Community Enterprise Promotion", which seem to be somehow related with the One Tambon One Product (OTOP) project.