The Kingdom of LanXang emerged in 1353 under Chao FaNgum, an exiled Lao prince who grew up in the Khmer court of Angkor. In 1353 FaNgum led his army to LuangPrabang to confront his grandfather, King Souvanna Khampong.
Unable to defeat his grandson on the battlefield, the aged king is said to have hanged himself and FaNgum was invited to take the throne.
LanXang Kingdom was born. It is portrayed in some accounts as stretching from China to Cambodia, and from Khorat plateau in present day northeastern Thailand to the Annamite mountains (Vietnam) in the East.
LuangPrabang became the capital of the kingdom of LanXang. King FaNgum made Theravada Buddhism the official religion. He married to the Cambodia king's daughter; Princess YotKeo Kaengkanya; and was given the gold Prabang (a golden statue and the most religious symbol of Laos) by the Khmer court. King FaNgum became known as "the Conqueror" because of his constant preoccupation with the warfare. Unable to to tolerate his warfare any longer, FaNgum's ministers finally removed him from the throne. Chao FaNgum then went to stay in Nan Kingdom in 1373 where he later died. He was 58 years old. (Today, Nan is a province of Thailand)
King FaNgum's oldest son, Prince Oun Heuan took the throne to become a second Lao king of the LanXang Kingdom. At the time, he was barely 18 years old. Three years later he gave the order to start counting his Kingdom's population. He was the first Lao king known to issue such (census) practice. The true result was not recorded or unclear but the record said that there were 300,000 (Sam Sen) Thai (Tai) men living in his Kingdom at the time. As a result he received a new honorable name from his ministers as King Samsenthai
The Tai are Lao which form different groups within a vast area of LanXang Kingdom at that time, including the Isan (northeast region of the present day Thailand). This does not include the ruling citizens in Thailand, that are of Siamese, Chinese, and Malay descent.
Further reading: Lao Monarch in each period, step-by-step.
