As pointed out in other posts, a visa is nothing more than permission to apply for entry to Thailand at an entry point. The IO makes an independent evaluation and decision to grant, or refuse, entry. That's pretty much the standard in most countries is far as I know.
As for shxttxyness of Thai immigration, my Thai wife and I maintain residences in the US and Thailand, and while I have been consistently treated in a professional manner on return to Thailand, the treatment of my wife by US immigration has often been abusive, even cruel. I guess the EU isn't like that.
(And thanks for the word shxttx. It's almost Shakespearean.)