when I still lived in the South of Thailand early 90ies we took people diving from Koh Samui, Koh Phan-gan, Koh Tao. The relationship between Thai's and the law is a strange one. It's almost like there are 2 systems. One for Thais one for "Farang".
A Thai would not dare to speak ill of the monarchs. They leave the room if a "farang" has had one too many and says something critical (they're peace loving but their love of peace might end there). This applies to both the very rich and the very poor.
We hired the captain from another region of the South to transport our divers. He was with the company since the day these islands were still 100% jungle and the place belonged to local fishermen. The reason why he left the region was because he had an argument and killed his neighbor. The deal was that he would not get killed only if he left the region and settled without ever returning to his family - this is considered not just shameful but seen as a huge disadvantage to make a living. They settled it without police, lawyer, bailiff, or judge, all among themselves.
Our other captain (in charge of the boat that left Koh Phangan) was also the right hand man of the most powerful person on the island. That guy was like a major, or village elder because he owned what was then the only "super market" on the island, and lot of the land. Our captain and "right hand man" to this guy was a devout monk (every year for several months left his wife to sweep the floor in silence in the monastery). He was a family man, highly respected within the community, and it was no secret among Thais that he was also heavily armed and had a body count of 12 people in his short life (late 20ies).
While murder is obviously illegal by law in Thailand, it is still used as a way by locals to settle disputes within rural areas of the South. The illegality isn't even considered here since in this case they see it as their moral duty which still trumps whatever some judge/lawyer's definition of justice is who has never before left Krung Thep.
Long story short it's quite complex to transform what is still in ways a tribal society into what we call "law-abiding" citizen. Especially when the law contradicts the values of society. And even more so when the existing police force is just a show for the tourists and to the urban population.