I can only speak for Phuket, people do get arrested and banged up, the police had quite a few check points around, Last year I know a guy (Thai) got stopped one night in Chalong he was over the limit he had a choice pay 40,000 baht at the roadside or go to jail and court in the morning, he said he will go to court in the morning, he got fined 5000 baht,