Prince Mongkut spent twenty seven years as a monk before his accession, and it was during that long monastic career, not after becoming king, that he grew convinced Thai monastic practice had absorbed syncretic and lax customs with no basis in the Pali canon, leading him to found the Dhammayuttika Nikaya in 1833 as a minority reform order built around what he judged to be a stricter, more textually grounded ordination and discipline than the mainstream Mahanikaya fraternity most Thai monks belonged to.
When Mongkut became King Rama IV in 1851, he did not abandon the reform order he had founded as a monk but continued to favour it, giving the Dhammayuttika Nikaya a close and lasting association with the Thai monarchy that has persisted long after his reign, even though the order has remained numerically much smaller than the Mahanikaya it was founded to reform. That royal association shaped the modern administrative unification of Thai Buddhism as well: later Sangha Acts brought both fraternities under a single national hierarchy headed by a Supreme Patriarch, formally coordinating two orders of very different size while leaving the Dhammayuttika Nikaya's disproportionate elite and royal influence within that structure clearly visible.