From the 3rd to the 14th century there was southward migration of ethnic T’ai (also known as Siam or Thai) from southern district of China called Nan Chau. At the beginning of 13th century, there were the establishments of some small kingdoms in the northern regions of the Khmer Empire. In 1279, the Sukhotei Kingdom was established and later on became Thailand. In 1353, at the northeast, Lan Xang Kingdom (Laos) was founded. Beyond the far northeast region of the Khmer Empire at the Chinese border, there was an establishment of a new state called Chao Chili by the Ytieh (Vietnam). Until the early 900’s, the state of Chao Chili was a vassal state of the Chinese Empire. After the formations of states and regaining independence, the wars began to take a toll on the Khmer Empire. The Thai moved south from the Sokhotei; the Chams and the Vietnamese from the northeast; causing the Khmer Empire to become very weak. Consequently, their territory became smaller and smaller as time went by. The last episode of this tragedy took place when Kampuchea Krom was incorporated into Vietnam rather than Cambodia in 1954.
After over one thousand years under the Chinese domination, the Vietnamese ambition on Territory expansion became unbearable to their weak neighbors in the south. The most well known campaign of all was Nam Tien (Southward Movement), which aimed at the Kingdom of Champa as their first target. As the campaign became reality, the southern border had been moved south as planned, Ly Thanh Tong (1054-1072), then renamed the country to Dai Viet (Great Vietnam). All of Vietnamese rulers continued to implement this campaign as their highest priority, and their border continued to open up to the south. While struggling for internal power, the Vietnamese always used the conflicts as opportunities to “borrow” neighbor’s territories for regrouping their forces or asking for asylum. When the wars were over, the grantor’s territory and their people would suffer great losses, not Vietnam. Besides, the Vietnamese leaders also used inter-marriage as another means of manipulation to capture their neighbors’ territories. The loss of Kampuchea Krom to Vietnamese was the result of these cunning practices. Champa and Laos have gone through the same experience, and the results were the undeniable facts of the recent world history.
The Khmers who live in the southern regions of the greater Cambodia are called Khmer Krom. The word Khmer Krom is more acceptable by the Khmer in Kampuchea Krom than the Khmer in Cambodia since it clearly identifies the geography of where these people were born, and live since 1862, upon completion of their occupation of Indochina, which included Tonkin, Annam, Laos Cambodia and Kampuchea Krom. The French colonial turned Kampuchea Krom to a colony and called it Cochin China, whereas the other four “states” were under the French protectorate. The name Cochin, perhaps, took after the southern city of India where both places have had much resemblance to each other. During their rule in Cochin China, the French authorities practiced a double standard policy when it came to the Khmer Krom and Vietnamese. The French avoided dealing directly with the Khmer Krom and used the Vietnamese to oppress them. Kampuchea Krom was the southernmost territory of the Khmer Empire. During this period, the Empire was a major power in South East Asia. The renowned architecture and construction of the Ancient Angkor Wat and many other numerous monuments in the Empire had brought the Khmer artistic to the highest level that human beings ever attained. The ruined port of Oc Eo (O Keo in Khmer) in the province of Rach Gia (today southern Vietnam), was the busiest port in the region, where the Khmers, Chams, Chineses, Indians, and Europeans did their trading. The township of Prei Nokor was a commercial center for the Khmer Empire, and it was once the most important military garrison against the Vietnamese’s southward movement. In spite of all these, the Khmer Krom people have outlived the sufferings and turbulence of the history, and remained united until today.