Preconditions for municipal status changes

Back when I still did not understand the difference between Tambon and Thesaban Tambon, I had run across a report titled "Urban Problems of the Chiangmai City" by Somsak Upapan, which amoung other things listed the necessary proconditions for an area to become a municipality of one of the three levels. Sadly, that website if no longer available, but luckily archive.org has the old version.

According to that report, the requirements for the different municipal levels are

• Thesaban Nakhon:
  • A population of 50,000 or more
  • A population density of 3,000 per km² or higher
  • Adequate amount of income to operate as a City Municipality according to the law
• Thesaban Mueang:
  • A population of 10,000 or more
  • A population density of 3,000 per km² or higher
  • Adequate amount of income to operate as a Town Municipality according to the law
  • Or be the municipality which contains the provincial court (or maybe it means provincial hall?)
• Thesaban Tambon:
  • A population of 7,000 or more
  • A population density of 1,500 per km² or higher
  • Revenue at least 12 million Baht
  • Approval of the citizen by a referendum

As I remembered only this from that text, this led to the confusion on whether Ko Samui conforms with the requirements to become a city, as it definitely does not has the population density required as of the above. Also, many of the TAO which have been upgraded to municipalities in the last two years don't pass that requirement, especially those in the mountainous areas have population densities much lower - for example That, Chiang Khan, Loei province has only 60 per km². This already led me to the conclusion that the population density requirement must have been dropped in the meantime, but I could not find any written proof of this so far.

When I now read that source again, I noticed one sentence which explains the same in another way:

There is no law specifying the number or density of population of an area to be upgraded as a Tambon Municipality except a broad outline saying it has to...

So all the above criteria are not fixed by law, but simply rules given to the committee deciding on the municipal changes, and thus it was easy to change them to allow upgrading the TAO which won't ever pass the population density criteria due to their size and type of landscape.

The above source dates back to 1998, so even before the upgrade of all the sanitary districts - off which most did not conform with those requirements either. So it's not too much surprising that a more recent source gives partially different requirements. The paper Recentralising while Decentralising: Centre-Local Relations and CEO Governors in Thailand in table 1 lists the same as above, only the population density for the subdistrict municipalities has decreased to 500 per km². The same number is also quoted in a very recent dissertation comparing the regional development in Satun and Perlis (Malaysia).