Some years ago when I bought my Nissan Teana, during my first few weeks with the red plate, police stopped me and told me the same thing about my red plate. He demanded to go to police station, or pay him some money to let me go. I paid him 300 Baht and he let me go. I contacted the showroom and informed the salesperson of the incident, and he just apologized for incident. I just forgot about it then.