Hòa Hảo
In 1956, Diệm recalled him to Saigon to help deal with the Hòa Hảo, a religious sect equipped with a private army. The Hòa Hảo was effectively an autonomous entity in the Mekong Delta, as its private army enforced a parallel administration and refused to integrate into the Saigon administration. While the Army of the Republic of Vietnam (ARVN) General Dương Văn Minh led the military effort against the Hòa Hảo, Thơ helped to weaken the sect by buying off its warlords.