If you are driving correctly and a policeman stops you and threatens to fine you for something you didn't do, whereby he just wants money, then take the ticket and go to the police department. That would be bad corruption. Note: I've never had such a bad experience with a policeman in Thailand, nor have many people whose stories I trust. The police in Thailand have usually been correct with me, and usually quite polite. I would bet there are bad cases, like most everywhere, but I've been pleasantly surprised by the nature of the police in Thailand by my own experiences, which is much better than the average traffic cop in the U.S. However, I do know many hot-headed people who have cursed the police for stopping them for gross violations of the law.