The Thanh Nhan Chinese made their living by exporting rice to other Southeast Asian countries, and their participation increased greatly in the years during the early 18th century after the Tây Sơn rebellion. Under local laws, rice exports to other countries were tightly regulated, but the Chinese largely ignored this rule and exported rice en masse. The prices of rice witnessed an increase of 50–100% in the 1820s as a result of these exports, which irked the Nguyễn court under Emperor Minh Mạng. Minh Mạng’s mandarin, Lê Văn Duyệt noticed that the Chinese had a great autonomy over trade affairs in Gia Dinh, which was partly attributed to the patronage of Trinh Hoai Duc who was serving as the governor of the province. Minh Mạng introduced a new series of measures to curb Chinese trade from 1831 onwards, and started by introducing new restrictions to which residents are banned from overseas travel, which culminated in a brief revolt among Gia Dinh’s residents in 1833. The Nguyễn court also experimented with measures to assimilate the Chinese immigrants; in 1839 an edict was issued to abolish the Chinese clan associations in Vietnamese-ruled Cambodia, which proved to be ineffective. Minh Mạng’s son, Thiệu Trị, introduced a new law to allow only Chinese-born immigrants to register with the Chinese clan associations, whereas their local-born male descendants are allowed to register with the Minh-Huong-xa and adorn the Vietnamese costume. The Nguyễn court also showed signs of subtle discrimination against people of Chinese origin; only one Minh Huong Chinese was promoted to a Mandarin. This sharply contrasted with the high representation of people of Chinese descent who were able to serve the Nguyễn court under Gia Long’s reign.
Chinese immigration into Vietnam visibly increased following the French colonization of Vietnam from 1860 onwards following the signing of the Convention of Peking whereby the rights of Chinese to seek employment overseas were officially recognized by the Chinese, British and French authorities. Unlike their Vietnamese predecessors, the French were very receptive of these Chinese immigrants as it provided an opportunity to stimulate trade and industry, and they generally found employment as laborers or middlemen. The French established a special Immigration Bureau in 1874 requiring Chinese immigrants to register with the Chinese clan and dialect group associations and eased trade restrictions that were previously in place. Historians such as Khanh Tran viewed this as a divide-and-conquer policy, and its implementation intended to minimize the chances of any Vietnamese revolt against the French authorities. The Chinese population witnessed an exponential increase in the late 19th century and more so in the 20th century; between the 1870s and 1890s, some 20,000 Chinese settled in Cochinchina. Another 600,000 arrived in the 1920s and 1930s, and peaks in the migration patterns were especially pronounced during the 1920s and late 1940s when the effects of fighting and economic instability arising from the Chinese Civil War became pronounced.