I'd love to know what country you come from, where there are no rules around drinking and its up to "self responsibility". In other countries (as you point out) they don't serve them if they drunk... doesn't work! All it does is shift some liability to bars after the fact. (and who decides if someone is drunk (ie over the limit) ! Very impractical in thailand!! As I'm sure you would agree, with a bit of common sense) )
DuI laws need to get tougher. But that ain't going to happen if you can buy your way out and Thais and foreigners treated differently.