The custom of giving peerages to Buddhist priests originated in Sri Lanka[1][2] and is believed to have been practiced in Thailand since the time of the Sukhothai Kingdom, during which the Sri Lanka's sect of Buddhism known as Laṅkāvaṃśa (Thai: ลังกาวงศ์) was prevalent in the region and it appears that Srī Śraddhā (Thai: ศรีศรัทธา; RTGS: Si Sattha), a nephew of King Pha Mueang, a local leader at that time, even travelled to the isle of Sri Lanka where he was ordained as a priest and was given a peerage.
[1] During the reign of King Mahathammaracha II of Sukhothai, the Buddhist community of Sukhothai was divided into two sects: araṇyavāsī (Thai: อรัญวาสี; RTGS: aranyawasi; literally "forest dwellers") and gāmavāsī (Thai: คามวาสี; RTGS: khammawasi; literally "village dwellers").
[1] It is also believed that senior monks had been appointed by the monarch of Ayuthaya as supreme patriarchs in charge of the entire monastic community.
[1] In the subsequent kingdoms of Thon Buri and Rattanakosin, the same custom was practiced until the enactment of the Sangha Administration Statute 1902 (Thai: พระราชบัญญัติลักษณปกครองคณะสงฆ์ รัตนโกสินทรศก ๑๒๑) by King Rama V, which established a Sangha Supreme Council to nominate monks to the monarch to be appointed to peerages.
๒๕๐๕),[1] except the appointment of the supreme patriarch which has been amended in January 2017 to solely be at the monarch's pleasure in line with the previous tradition.