Thơ was thrown into a crowded cell with several other prisoners that had no light or toilet and filled with their own excrement. One of his cellmates was Dương Văn Minh, then a junior officer in the French military forces with whom he would work over the next two decades. Thơ was released first and lobbied to have Minh released as well and the pair remained close friends. Following World War II, Thơ became Interior Minister in the French-backed State of Vietnam under former Emperor Bảo Đại. Following the withdrawal of France from Indochina after the Battle of Điện Biên Phủ, Vietnam was partitioned into a communist north and anti-communist south. Following the proclamation of the Republic of Vietnam—commonly known as South Vietnam—by President Ngô Đình Diệm, who had dethroned Bảo Đại in a fraudulent referendum, Thơ was appointed the inaugural ambassador to Japan. Despite spending most of his time in Tokyo confined to his bed by a fractured hip, Thơ secured reparations from Japan for its imperial occupation of Vietnam during World War II. 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. However, one Hòa Hảo commander, Ba Cụt, continued to fight, having had a personal history of bad blood with Thơ's own family. The orphaned, illiterate Cụt's adopted father's rice paddies were confiscated by Thơ's father, which purportedly imbued Cụt with a permanent hatred towards the landowning class. Cụt was eventually surrounded and sought to make a peace deal so he sent a message to Thơ asking for negotiations so that his men could be integrated into mainstream society and the nation's armed forces. Thơ agreed to meet Ba Cụt alone in the jungle, and despite fears the meeting was a Hòa Hảo trap, he was not ambushed. However, Cụt began asking for additional concessions and the meeting ended in a stalemate. Cụt was captured on 13 April 1956 and guillotined after a brief trial and his remaining forces were defeated in battle. During