They could also have introduced land reform which would have undermined the Norths position.
But they did introduce land reform (though it's effectiveness was minimal):
In South Vietnam, especially in Mekong Delta, landholdings in rural areas were concentrated in small number of rich landlord families. Thus, it was urgent to implement land reform in South Vietnam. Diệm had two attempts to control the excesses of the land tenancy system by promulgating the Ordinance 2 on 28 January 1955 to reduce land rent between 15% to 25% of the average harvest and the Ordinance 7 on 5 February 1955 to protect the rights of tenants on new and abandoned land and enhancing cultivation. In October 1956, with the urge from Wolf Ladejinsky, Diệm's personal adviser on agrarian reform, Diệm promulgated a more serious ordinance on the land reform, in which he proclaimed a "land to the tiller" (not to be confused with other Land reform in South Vietnam like Nguyễn Văn Thiệu's later 'Land to the Tiller" program) program to put a relatively high 100 hectares limit on rice land and 15 hectares for ancestral worship.[83] However, this measure had no real effect because many landlords evaded the redistribution by transferring the property to the name of family members. Besides, during the 1946–54 war against the French Union forces, the Việt Minh had gained control of parts of southern Vietnam, initiated land reform, confiscated landlords' land and distributed it to the peasants.[84] Additionally, the ceiling limit was more than 30 times that allowed in Japan, South Korea, and Taiwan, and the 370,000 acres (1,500 km2) of the Catholic Church's landownings in Vietnam were exempted. The political, social, and economic influences of the land reform was minimal.[85] From 1957 to 1963, only 50 percent of expropriated land was redistributed, and only 100,000 out of approximately one million tenant farmers in South Vietnam benefited from the reform.[86]