The martial art of Thailand and primarily practiced as a sport today it has become one of the essential training arts in MMA due to its effectiveness in the ring coming from profesional competitions. The original art Muay Boran is a much more inclusive art which incorporated various locking and grappling techniques as well as weaponry. Training techniques from Muay Thai are incorporated as well as training the "clinch" range incorporating knees and elbows.
Resource Link
Outline of Training Methods
Strikes
Pad Training
Clinch Training
