This image is from the site of the Coalition of Vietnam Nationalist Parties. Several images of the flag appear, but it appears to be rectangular at times and within the site there is a square version of the flag. This organization is devoted to undermining the communist government in Vietnam. Phil Nelson, 7 May 1999
The Coalition of Vietnam Nationalist Parties is composed of Vietnamese organizations in exile and underground organizations in Vietnam. Their purpose is the liberation of Vietnam. Purportedly, they have been involved in several covert operations in Vietnam.