The Đảng Dận chủ Xã hội Việt Nam (English: Viet Nam Democratic Socialist Party) was a political party in South Vietnam. It was founded established on 21 September 1946 (other sources mention 1944) by Huỳnh Phú Sổ, the founder of Hòa Hảo. The party was formed through the unity of a sector of socialist-minded people in Saigon and some provincial sect leaders. The party was persecuted by the Việt Minh. Huỳnh Phú Sổ was killed by the Việt Minh in 1947, after which the party was dissolved. In February 1955, General Nguyễn Giác Ngộ of Hòa Hảo claimed that the party had been revived. The party obtained three seats in the 1959 National Assembly election.
It is common practice to associate the religious flags with their respective armed and/or political movements in Viet Nam (i.e. Đạo Cao Đài) since at some point in time they had autonomous military branches and/or supported the movement for independence.
So, in essence, the Viet Nam Democratic Socialist Party flag is that of the Hòa Hảo. Esteban Rivera, 27 February 2018