Maps of Thailand and Isaan ...

[goji]

I have been around to so many places, I often ask for district as well. That weeds out foreign boys as well; I'm not good at recognizing accents, so a boy from Cambodia could pass as coming from Surin, but when I ask for his district, the truth will come out.

How often do foreign boys try to pass themselves off as Thai ?

The only way I can check is by the ID document & I don't recall a case of one lying about his country of origin.

[frequent]

How often do foreign boys try to pass themselves off as Thai ?

I've never encountered one; quite the reverse

[pong]

How often do foreign boys try to pass themselves off as Thai ?

The only way I can check is by the ID document & I don't recall a case of one lying about his country of origin.

Not that often. These are 2 most frequent, or rather If it happens its from there:
real Lao guys who fake /deny this and tell them theyre Isany. Very rarely also Khmer guys pretend to come from Surin (where Khmer is more spoken as Lao=Isany)
Much more notorious and sometimes warranting to vigilance are the hilltribeys, notably the Shan/Karyen who take the issue of nationality not that serious anyway. (thats the way I like it to take all the burocrazyness anyway). Their own widely held view is that they are entitled to have their very own nation. Though all know that a Thai ID is much better as a Burmese, even if its just the pinky. And lending out IDs or swapping them or whatever is also widespread-in the black market you can fairly easily arrange that. An awful lot of Thai IDs get stolen/lost/whatever, that makes them invalid for real officialdom (thats why they are chipped) but still very usefull for not so serious goals.
(in my home country they now even check the ID-among the best secure in this world already- in banks when you come for a little more serious bisnis, like transferring the big sums for a new house. Check for it being stolen/missing and for it to be genuine real with some secret devices.