What is the Mongkhon?

In a Muay Thai fight, the two fighters (Thai or Farang) during the pre fight prayer called Wai Kru, must wear a string (cord) around their head called Mongkhon and also strings on the forearms called Pra Jiad.
Those two objects are symbols of protection and origin of the fighter. The Mongkhon (or Mongkhol) is unique in Muay Thai and cannot be worn in Cambodia and Burma.
The Wai Khru is a Muay Thai tradition, a parayer accompanied by body movements that symbolize the fighter’s gratitude towards his Master and a way of concentration before the fight.
Looking deeply into Muay Thai history the Wai Khru symbolizes also respect to the event chairman or to the HM the King since in the past He used to spectate almost every event.

Video of a Mongkhon blessing: