Number of foreigners in Thailand

Last year, the annual report of the registered population added new columns which list the number of citizen with Thai nationality and the registered foreigners - those who have to go through the bureaucratic 90 day reporting. As this data is listed not just for the whole country but also for each province, its a relatively easy thing to display the percentage of non-Thai citizen on a map of Thailand. This way to display directly shows that the majority of foreigners in Thailand are not the western expats, or business men working in the capital, but the highest percentage is found in the two border provinces Mae Hong Son and Tak, the highest absolute numbers in Chiang Mai and Chiang Rai, hinting that its mostly refugees and migrant workers from Myanmar.

Province	Total	Foreigners	Percentage
Tak	631965	102393	16.2%
Mae Hong Son	275884	43918	15.9%
Chiang Rai	1282544	118407	9.2%
Chiang Mai	1735762	130043	7.5%
Bangkok	5686646	94571	1.7%
Yasothon	539815	262	0.0%
Thailand	65931550	834645	1.3%

The lowest percentage and absolute number is found in Yasothon - as can be seen in the map, most of the northeast and north have less than average foreigners. Even though this population data isn't published in the Royal Gazette yet, I have used the numbers as of December 31 2016, which can be found at the statistics page of DOPA.

To confirm the assumption that its mostly people from Myanmar, one has to look into the census 2010, which includes the list of nationalities found in each province. For the whole country, 1292862 people from Myanmar were counted, 281321 from Cambodia, 141649 from China. The only other groups above 100000 are those of "other country" (120699) and those with unknown nationality (117329).