From my understanding they have gentlemen rules they follow like in most fighting sports .
Thai boxers are known for being extremely respectful outside of the ring. You will never see a Thai boxer bad-mouthing his opponent(s) like you see in the Western Boxing world. Thai's believe in doing all their "talking" in the ring, letting their fighting speak for them.techniques that are considered "dirty pool", but are still ring legal.
No1- When a mid-body level kick comes, you can trap and spike it with your elbow.
No2- When clinching your opponent, get your glove into his face and cover his nose and mouth so that he has difficulty breathing.
No3- Also, while clinching, use your chin to dig into your opponents face, especially the eyes. Thai boxers like to enter the ring with a few days razor stubble for two reasons. One, the stubble helps punches, elbows, etc slip off the face, and two, to dig it into their opponents face.
No4- Again, during the clinch (notice a trend?), when fighting for control of an opponents neck/head, or defending from having your head pulled down, you can reach across his face and jam your elbow into it. Use your elbow/arm as a stiff barrier, keeping it in his face. Dig it into his nose or eyes or mouth...
No5- Again, while clinched, you can wrap your leg around your opponent and heel kick him in the back of the leg or buttocks.
No6- Throw a haymaker-like punch, but hit him with the bony part of the wrist rather than the fist. This is a good knockout technique because the wrist/forearm area is not protected with boxing gloves.
No7- Like boxing, it is illegal to hit an opponent who is down. However, if the opponent has not hit the floor yet... I have seen many fights ended when an opponent gets that extra kick or even a knee in before their opponent hits the floor after they have thrown or dumped them.
No8- Push Kicking opponent in the face. This is the most insulting thing you can do in the ring. You would not make a Thai as angry if you said very explicitly derogatory remarks about his parents. In Thai culture (and many Asian cultures) the head is considered the most important part of the body (practically holy!), the feet the lowliest. To push kick them in the face is to say that you are beneath the
dirt under my feet. When a Thai push kicks to someone's face, he does not strike with it, rather he brushes his opponents face with it, heightening the insult factor.
As you can see, Thai's like to play for keeps. However, they keep it in the ring. The above techniques are all legal in the ring, but considered to be "dirty pool". Most fighters refrain from using them, as they can expect like treatment if they do. As an interesting note along the same idea, this is why many, many Thai fighters rarely ever use elbows in the ring. There is sort of a "gentleman's agreement" amongst boxers that if you do not use elbows, neither will I. If you do, however, expect like in return. This from the book mauy Thai. The art of fighting. Written by
Yod Ruerngsa, Khun Kao Charuad and James Cartmell