Muay Thai started back in the Medieval Ages. As the Thai tribe immigrants emigrated from the South of China they had to hide from attackers and met with resistance from local people. In their fight for survival, the Thai had gone through countless battles and many lives had been lost. Their wars were fought using bows and arrows, swords, and pikes. However, during hand-to-hand combat weapons become clumsy; arms, legs, knees, and elbows were used as weapons. This must have been extremely successful, as it was then developed into a form of Martial Arts used in battle. This was the origin of Muay Thai.

When the Thai settled down, built a city, and extended their lands there was a need for an army to defend that country. Soldiers had to learn Muay Thai along with traditional weapons. Various tactics for attack and defense were developed, they were called "boxing tactics". Later, the commoners began to train in Muay Thai for self-defense, and a qualification to become a soldier.

The Ayudhya Period, was a period of consecutive fighting against the neighboring countries of Burma, Cambodia and Vietnam. Under King Naresuan (1560 A.D.) every soldier trained in Muay Thai as did the King himself. During one of the many battles between Burma and Siam, the king was captured. The Burmese knew of his prowess as the best unarmed fighter in the realm and gave him a chance to fight with their best for his freedom. Upon his return to Siam he was hailed as a hero and Siamese-style boxing, as it was called then, was soon recognized as a national sport. The change in the art was to continue under another fighting King, Sri San Petch; also known as Prachao Sua (the Tiger King). He loved Muay Thai so much that he often fought incognito in village contests and temple fairs, beating the local champions and becoming quite a legend in his own time.

When Ayudhya fell in 1767 A.D., many Thai became Prisoners of War. In 1774 a very famous fighter named Nai Khanomtom was captured along with other Thai prisoners. He was brought to Rangoon in Burma, where Mangra, the King of Burma was curious to see how the various fighting styles of Burma and other countries would compare. Nai Khanomtom was selected to fight against the Burmese champion. Nai Khanomtom did a pre-fight dance called Wai Kru which puzzled all of the Burmese. When the fight began, he charged out, and using punches, kicks, elbows, and knees, quickly pummeled the Burmese. The people believed that the Burmese opponent was distracted by the Wai Kru, so the knockout was invalid. The King then asked if Nai Khanomtom would fight nine other Burmese champions to prove himself. Nai Khanomtom defeated them all in a superior fashion. King Mangra was so impressed that he remarked, "Every part of the Thai is blessed with venom. Even with his bare hands, he can defeat nine or ten opponents. As his lord master was incompetent, the country was lost to the enemy. If his lord were any good, there was no way the City of Ayutthaya would fall." He offered Nai Khanomtom freedom along with either riches or two beautiful Burmese wives. Nai Khanomtom chose the wives as he said that money was easier to find. He then departed with his wives for Siam.

During the reign of King Rama VII in the Revolutionary Period, permanent boxing stadiums were established both in Bangkok and the provinces. They gradually disappeared in 1942 during World War II. After the war, boxing stadiums sprang up overnight. Skilled boxers from up-country flocked to Bangkok to take part in tournaments. Finally the first standard boxing stadium was established, the Rajdamnern Stadium, in 1945. Rules were set and regular bouts were set at 5 rounds of 3 minutes each, with a two-minute interval between rounds.

Muay Thai is still developing, but what remains unchanged is the use of the pipe and drums as musical accompaniments for the matches. This is considered a unique characteristic of Muay Thai.

Many additions have been made to the regulations of Muay Thai. It is now forbidden to hit the private parts since this technique has become quite infamous as a form of attack and is considered a disgrace for the fine art of Thai Boxing. Today Muay Thai still remains a national art form of Thailand.