How many expats do you reckon there are in Thailand? How can I find this information out?

I'm here

+1 to your list

Interesting question, and probably hard to find a reliable source. As a start, this site

http://www.justlanded.com/english/Common/F...xpats-are-there

gives the total worldwide population of expats of around 200 Million. Some countries are specifically listed (eg. USA with 38 Million), but no mention of Thailand.

Of course you need to specify a definition of expatriate. Would you include all the illegal workers from neighbouring countries - which probably top the list numerically. Dunno, but maybe 2+ Million?

Immigration must have a rough idea of how many foreigners are in Thailand at any one time . . . but how to differentiate from the 1 week or 1 month tourist and all the other categories - when does one become an ex-pat? eg someone on a 12mth education visa? marriage visa? retirement visa? and of course the (and I guess htere are many thousands) people doing regular border runs who would presumably show up as 15 or 30-day 'tourists' despite maybe having been here for years.

And one more - what countries would you count as ex-pat being from? Ukraine? China?

I think it's an impossible task!

Immigration must have a rough idea of how many foreigners are in Thailand at any one time . . . but how to differentiate from the 1 week or 1 month tourist and all the other categories - when does one become an ex-pat? eg someone on a 12mth education visa? marriage visa? retirement visa? and of course the (and I guess htere are many thousands) people doing regular border runs who would presumably show up as 15 or 30-day 'tourists' despite maybe having been here for years.

And one more - what countries would you count as ex-pat being from? Ukraine? China?

I think it's an impossible task!

Quite. So you'd need to define what an expat is. Maybe people doing 90 day reporting? (ie legally here). I think 90 day reporting is required for all longer visas but would exclude anyone (illegally?) on a tourist visa.