Quang started as a non-commissioned officer (NCO) in the French colonial army and was later promoted to Emperor Bảo Đại’s aide-de-camp, then commander of his personal Imperial Guard.

According to common rumors, Quang had "a virtual monopoly on the economic life of the Delta," ran a "brisk trade in rice and opium," and had amassed a small fortune through official corruption.

[3]: 116 On 23 November 1966, at the urging of Prime Minister Nguyễn Cao Kỳ he was replaced as IV Corps commander by Major General Nguyen Van Manh.

Yet Kỳ's charge of corruption appeared to be accurate; Quang had amassed considerable wealth through the sale of offices, furthering the financial interests of his wife and relatives.

[4]: 14–5  However following the Battle of Ban Me Thuot in March 1975 he failed to inform the CIA of Thiệu's plan to abandon the Central Highlands, jeopardizing the evacuation of Americans and their South Vietnamese staff.