The link to this file is titled "รหัสองค์กรปกครองส่วนท้องถิ่น สำหรับลงทะเบียนฝึกอบรม", which means "code of local administrative organization for register training". It contains all of the local government entities in Thailand (except of Bangkok), with the code (รหัสอปท.) in the first column, name and type (ชื่ออปท.) in the second, and province and district in the last two. The file is relatively recent, according to the file information stored by Excel itself it was created in October 2008.
The interesting part is of course the codes, which are created according to the following scheme
- 1st digit: Type of the local government
- 2 = Provincial Administrative Organization (PAO, อบจ.)
- 3 = City Municipality (เทศบาลนคร), also including the special administration of Pattaya (อปท.รูปแบบพิเศษเมืองพัทยา)
- 4 = Town Municipality (เทศบาลเมือง)
- 5 = Subdistrict Municipality (เทศบาลตำบล)
- 6 = Subdistrict (Tambon) Administrative Organization (TAO, อบต.)
- 2nd and 3rd digit: the geocode of the province, as defined by TIS 1099:2548 and DOPA
- 4th and 5th digit: the geocode of the district, in case of the PAO it is 01
- 6th and 7th digit: simple counting of the entities
The number in the third column is the geocode as defined by DOPA for the subdistrict which corresponds with the TAO. I am not sure if this list is supposed to become the official geocodes for the local government units, but if they intend this I don't think it'd be a good idea. Especially including the type into the code is a bad idea, as all of the municipalities and TAO change their type with time. Then with an upgrade the code has to change, and even though the entity stayed the same it gets a new code. Making this code the first digit even makes it difficult to sort, unlike the DOPA geocodes geographically related units don't have numbers closeby. And additionally these codes don't fit together with the codes issued by DOPA, or the municipality codes I found earlier.
Due to the plain numbering of all entities of one kind in one district, the TAO also loose the connection to the corresponding subdistrict. Even though TAO and Tambon are two different things, it'd make sense to have a code for the TAO which make it easy to get to the Tambon code.
I also spotted one mistake in this list already - the city of Surat Thani has the code 4840101, however according to the scheme one would assume it to have 3840101.