When Huynh Phu So began teaching in the Mekong Delta village of Hoa Hao in 1939, his reform did not add new revealed material to existing Buddhist practice, the pattern followed by many of the era's new religious movements, but stripped elements away. Elaborate temple ritual gave way to worship at a plain home altar. Monastic intermediation between the layperson and religious practice was reduced sharply in favour of direct personal cultivation. Most strikingly, early Hoa Hao teaching rejected the use of physical images in worship altogether, a deliberate break from the visual culture of conventional Vietnamese Buddhist practice, in which Buddha images are central to temple and household devotion alike.
The reform's appeal lay substantially in that simplicity. A rural Mekong Delta population could take up a demanding but accessible practice, centred on personal ethical cultivation, filial piety and ancestor veneration, without needing sustained access to monastics, temples or elaborate ritual apparatus. The movement spread rapidly through the delta in the years immediately following its founding, growing into one of the largest homegrown religious movements in twentieth century Vietnam. Its reformist character is also what most clearly separates it from Cao Dai, the other major new religious movement of the same region and era: Cao Dai built outward, synthesising Buddhism, Taoism, Confucianism, Catholicism and folk religion into one deliberately composite system, while Hoa Hao built inward, reforming an existing tradition from within rather than combining it with others.