Because in Thailand there are 2 laws, one for the Thai, they can do whatever they want without being afraid of repercussion, if you are a farangs get your wallet ready. I don't know how many times I went thru road blocks and they told me I was speeding, no radars of course, I gave them 200Bahts and they let me go. How many Thais are driving under age, no permit. One time the cop was giving a ticket to a farangs for not wearing a helmet on his motorbike, in the meantime, his body the cop was stopped at the red light, no helmet. You wouldn't see that in my country or any civilized country.