The historic peoples of Southeast Asia began arriving some 2,500 years from China, Tibet, and the Indian sub-continent. During the second Asian migration, tribes of Burs, Chams, Khmers, Mons, Shans and many more ethnic groups, traveled away following the Indo-china trade route and began to settle in areas South of the Himalayas and North of Kunluns.
Keeping many of their traditions and cultures, and forming themselves into strong warrior tribes, they usurped or absorbed the aboriginal groups on their travels, reaching fertile lands of Southern China, before moving on, and dominating most of central and South East Asia.
The Burs, (Burmans related to Tibetans) arrived from Tibet before the 9th century, displacing earlier cultures, and a Buddhist monarchy was established by the 11th. century, was conquered by the Mongols, and ruled by Shans in the 12th century.
From the southern tip of Indochina the Kingdom of Funan traded as far west as Persia. It was absorbed by Chenla, itself conquered by the Khmer, who date as far back as the 1st. century A. D. and culminated in the great Khmer empire which flourished from the 9th century to the 13th century, encompassing present day Thailand, Cambodia, Laos and S. Vietnam.
The Nanchaoi Thai tribes, began migrating from the Southern China region in the 11th. Century, reducing the Khmers, Chams a encompassing present day Thailand.
A. D. 733, The area of present day Yunnan and southern Szechwan in southern China was inhibited by a Thai group known as the Shan in the eighth century. The Shan acknowledged the suzerainty of China. A Shan Prince gained control over neighboring territory and proclaimed himself king of Nanchao (“Southern Princedom”). The emperor confirmed his title, and the king continued to pay tribute. When his son ascended the throne, he refused to be subservient to China. Although Chinese Imperial forces clashed several times with Nanchaoan troops the Chinese emperor tried to overpower the new Nanchaoan king, but could not prevail. In A. D. 774 China formerly recognized Nanchao as an independent state. Meanwhile, the Tibetans taking advantage of internal difficulties within the Chinese Empire continually invaded its western provinces.
In one early raid they succeeded in reaching the capital at Chang-an (Sian), which they seized and sacked. Chinese imperial troops sometimes defeated them, but the Tibetan forces would then retreat back to their mountain fortresses.
In A. D. 798, the Chinese Tang emperor concluded an alliance with a Muslim chieftain in the west and the support of the Nanchaoans against the Tibetans. With the help of these powerful allies, the Tibetans were eventually decisively defeated and in 821 were forced to agree to a treaty of peace with China. The kingdom of Nanchao thrived for 600 years
When the Shans in northeast Burma, overthrew the Mongol puppet government at Pagan on the Irrawaddy river, a small Mongol army was dispatched to reestablish control of the area. At the fortified three-walled town of Myinsaing, Shan forces checked the Mongols of whom 500 were killed in battle The Shan leaders fearful of possible Mongol reinforcements, offered the Mongol commander a bribe; he accepted it and withdrew his army to Yunnan province in southwestern China. Later, the Mongol commander was executed by Yunnans governor for his actions; the Mongols however, decided not to invade again.