I understand. Because, to get into the Schengen area, as a Thai, you need a very expensive visa and a pile of documents. (Not that the average Thai can afford that).
It pisses them off (and me too, because of course I paid for it this year for my GF)...
Secondly, there are Farang out there 'using' the system. They know that. The officers are getting more alert.
And lastly. It does not matter what the rules are and how many runs you have done. It all depends on the attitude of the officer...