There is a phrase about Muay Boran that states, "Punch Korat, Wit Lopburi, Posture Chaiya, Faster Thasao. As well as continuing to function as a practical fighting technique for use in actual warfare, Muay Thai became a sport in which the opponents fought in front of spectators who went to watch for entertainment. This kind of muay contests gradually became an integral part of local festivals and celebrations, especially those held at temples. It was even used as entertainment to kings.
Eventually, the previously bare-fisted fighters started wearing lengths of rope wrapped around their hands and forearms. This type of match was called muay kaad chuek

Muay Thai consisted of an arsenal of nine weapons-the head, fists, elbows, knees and feet-known collectively as na-wa arwud. However in modern Muay Thai, both amateur and professional, head butting an opponent is no longer allowed.
Note: when Muay Thai fighters compete against fighters of other styles (and if the rules permit it), they almost invariably emphasize elbow (sok) and knee (kao) techniques to gain a distinct advantage in fighting. Almost all techniques in Muay Thai use the entire body movement, rotating the hip with each kick, punch, elbow and block. The rotation of the hips in Muay Thai techniques, and intensive focus on "core muscles" (such as abdominal muscles and surrounding muscles) is very distinctive and is what sets Muay Thai apart from other styles of martial arts.