There's no official grading in Muay Thai....only a fight record. The head bands and arm bands are worn before the fight during the traditional 'wai kru,' which is a dance that is performed before the start of each bought by the fighters. It dates back hundreds of years to a war between Thailand and Burma. Check out www.tigermuaythai.com
Thailand's doing it's best to bring Muay Thai and MMA together.