@Pete ******
I agree there are no standard checks on requirements at the border, but in less than a percent there are checks, and the requirements exist.
And that is quite logical of course.
When you get a visa to visit cooking class in Thailand, there is no reason anymore to enter Thailand when the cooking class is finished, so why should they let you in?
On the other hand, if you abuse the visa this way, you normally will get away with it without any problems.