In the mid-1970s, the number of Vietnamese in Thailand was estimated at between 60,000 and 70,000, most of them in the Northeast. Three broad categories of Vietnamese were in the country. The first were the descendants of persons who fled from political upheaval and persecution during the precolonial era in the late eighteenth century and through much of the nineteenth century. Most of them settled either in Bangkok or in the area southeast of it, and many of their descendants were absorbed into Thai society, although some still lived in villages that were identifiably Vietnamese. Many who came in the nineteenth century were refugees from anti-Catholic persecution by rulers in Cochinchina (southern Vietnam, around the Mekong Delta) before the French established political control over that area. The second category consisted of persons who opposed the establishment of French domination over all Vietnam in 1884 and presumably expected their stay in Thailand to be short. With some exceptions, however, their descendants and those of other Vietnamese who came to Thailand in the first decades of the twentieth century remained. The earliest arrivals in this category, like their predecessors, mostly came to southeast Thailand. Later immigrants tended to go to the Northeast. The third category included those who fled from Vietnam between the end of World War II in 1945 and the consolidation of North Vietnamese rule over all of Vietnam in 1975. For those who came after the Second Indochina War had ended, Thailand was simply a way station en route to somewhere else, usually the United States.
Most of the 40,000 to 50,000 Vietnamese who came in 1946 and shortly thereafter were driven from Laos by the French, who were then reimposing their rule over all of Indochina. More Vietnamese came later, and, like those who came in the 1920s and 1930s, they expected to return to Vietnam. Between 1958 and 1964 (when the intensification of the war in Vietnam inhibited their return), arrangements were made for the repatriation of Vietnamese to the Democratic Republic of Vietnam (North Vietnam), and an estimated 40,000 left Thailand. Over the years a few families went to the Republic of Vietnam (South Vietnam). The movements of this period, both voluntary and involuntary, left between 60,000 and 70,000 Vietnamese in Thailand, an undetermined portion of which were post-World War II migrants who could not or would not return to their homeland.