I am aware of the purges of French people after the French were defeated in Vietnam / Indochina. French-owned plantations were nationalised after the American Vietnam War and most French were either killed or kicked out.
But is there still a group of descendents living in that region, either as a business elite or a rural farming community of any significance (i.e. Caldoches number over 70,000)? And what is their name?
Indochina was never a settler colony like New Caledonia and Algeria, so it did not have a sizeable French population: a 1940 census shows that there were 34000 French people in a total population of 22.6 million (so about 0.15% vs 13% for Algeria in 1959). Those people mostly lived in the large urban centres, and a good proportion of them worked for the administration or were in the military. Compared to Algeria and New Caledonia, where settlers had started to arrive in the mid-19th century, the French population was recent. It was also largely male at first: the 1902 census in Cochinchina mentions 4000 men and 1000 women. It got better later when women were encouraged to move to Indochina, but the sex-ratio remained skewed (38% women according to the official statistics of 1937). Commercial rubber plantations only began in the 1900 and, by the 1940s, 2/3 of the hevea cropped area was owned by French holding companies (Michelin, Banque de l'Indochine, Rivaud-Hallet): there were only 63 plantations owned by French families, and they were rather small (30-50 ha).
So there were just not enough European people in French Indochina with multi-generational roots to form a culturally distinct population like the Pieds-Noirs in Algeria. In the 1960s, France was no longer militarily and politically active in Vietnam, but kept a strong economic and cultural presence in the South until 1975. There were about 11000-17000 French people, including mixed-race (métis) and naturalized families, possibly half of them. These people fled to metropolitan France in several waves: after WW2 due to the chaos of the 1945-1946 period, after 1954 when all but a handful of French people were expelled from the Democratic Republic of Vietnam (some moved to South Vietnam but many were repatriated), during the Vietnam war, and in 1975 after the fall of Saigon. Were there some native French people left in Vietnam after that? Apart a few diplomats and (possibly) a couple of activists, no.
The question of the métis, however, was not fully resolved. In the 1950-1960, there were efforts to "repatriate", somehow forcefully, métis children of unknown French fathers (notably those of French soldiers and born during the Indochina War), but some were left behind. By the late 1970s, the Vietnamese government considered the few métis left to be unassimilable and wanted to get rid of them (Saada, 2007). This was not easy. In 1980, a group of métis people in Ho-Chi-Minh-Ville, representing 3000 families, sent a petition to French authorities asking to be repatriated, but they were turned down as they were born before 1945. In any case, there were no significant French presence in Vietnam after 1975. I'm less familiar with Laos and Cambodia, but the French were even less present there during colonisation, so there's no reason for ethnic French being there in significant numbers after independance.
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