We went to the Cao Dai Holy See yesterday. Caodaiism is a home grown Vietnamese religion that blends elements of Christianity, Confucian, and Buddhism. It's a syncretistic, monotheistic religion. Their saints include Buddha, Confucius, Jesus Christ, Muhammad, Pericles, Julius Caesar, Joan of Arc, Victor Hugo, and Sun Yat-sen. By any definition, a pretty diverse group. As world religions go, Cai Dai is a baby. It wasn't founded until 1926 in Tay Ninh.
There are anywhere between 2 million and 6 million Cao Dai adherents. Almost all of them are in Vietnam, though there may be 30,000 adherents in Europe and the US following the Vietnamese diaspora of the late 1970's. The Cao Dai have had a stormy history in Vietnam. They battled the French in the colonial wars and fought against both the Communists and Vietnamese regimes supported by the US until 1975. Cao Dai were persecuted by the Vietnamese government until 1997.
The Cao Dai have a large role in Graham Greene's "The Quiet American." Graham portrayed them as a "third force," neither Communist nor colonialist, that could guide Vietnam in the post colonial world. That didn't work out to well.
There are more photos of the Cao Dai in my archive and available from ZUMA Press.