Thoroughly discouraged by 1967, he confided to Edward G. Lansdale, who was then serving as US Ambassador Ellsworth Bunker's assistant, that the army was "far more corrupt than anyone can imagine" and that "the 'Americanization' of the military effort was accepted by many ARVN leaders as an excuse to spend more of their time on personal, selfish affairs."

Frustrated with his job, a young officer spent increasing amounts of time at cafes and bars, gradually developing a series of relationships with local mistresses until one became what the Vietnamese called "the second wife."

At the same time, to impress and satisfy the needs of both wife and mistress, and his families and friends, the officer gradually began using his position to acquire property, houses, and material goods, all of which demanded a constant supply of cash.

His revolutionary development teams were busy throughout South Vietnam, working in thousands of villages and hamlets, where local army province and district chiefs had little control over their activities.

To further strengthen his political position in 1966, Kỳ also tried to transfer the Territorial Forces command from the Joint General Staff (JGS) to Thắng's Ministry of Revolutionary Development.

[1]: 256–7 In July 1967 in an effort to increase his position before the 1967 South Vietnamese presidential election Kỳ proposed that Thắng, be put in charge of an enlarged Political Warfare Department.

[1]: 265  On 15 August 1967 Kỳ, Viên and Thắng met with COMUSMACV General William Westmoreland, Civil Operations and Revolutionary Development Support (CORDS) Director Robert Komer and Bunker to discuss specific aspects of the reorganization.

Ky wanted to make Thắng vice-chief of staff of the army, with responsibility for the Territorial Forces command, the Military Security Service, and the Political Warfare Department while retaining control of the revolutionary development cadre.

He also proposed assigning province and district chiefs directly to the political warfare agency under Thắng and having the Military Security Service spearhead a major effort to end corruption in the armed forces.

Although Thắng verbally agreed to accept the post of vice-chief for territorial security on the JGS, he remained minister of revolutionary development and never assumed his new staff duties.

No friend of Thiệu, as revolutionary development minister, he had been habitually frustrated over Saigon's unwillingness to replace corrupt or ineffective officials and had complained loud and often about its neglect of area security.

Westmoreland was extremely pleased by the move, calling it "the most important single appointment that has been made in the last year," and for the next few months Thắng proved himself an able military leader as well as a competent civil administrator.