Thai rulers were absolute monarchs whose office was partly religious in nature. They derived their authority from the ideal qualities they were believed to possess. The king was the moral model, who personified the virtue of his people, and his country lived at peace and prospered because of his meritorious actions. At Sukhothai, where Ramkhamhaeng was said to hear the petition of any subject who rang the bell at the palace gate to summon him, the king was revered as a father by his people. But the paternal aspects of kingship disappeared at Ayutthaya, where, under Khmer influence, the monarchy withdrew behind a wall of taboos and rituals. The king was considered chakkraphat, the Sanskrit-Pali term for the "wheel-rolling" universal prince who through his adherence to the law made all the world revolve around him. As the Hindu god Shiva was "lord of the universe," the Thai king also became by analogy "lord of the land," distinguished in his appearance and bearing from his subjects. According to the elaborate court etiquette, even a special language, Phasa Ratchasap, was used to communicate with or about royalty.
As devaraja (Sanskrit for "divine king"), the king ultimately came to be recognized as the earthly incarnation of Shiva and became the object of a politico-religious cult officiated over by a corps of royal Brahmans who were part of the Buddhist court retinue. In the Buddhist context, the devaraja was a bodhisattva (an enlightened being who, out of compassion, foregoes nirvana in order to aid others). The belief in divine kingship prevailed into the eighteenth century, although by that time its religious implications had limited impact.
One of the numerous institutional innovations of King Trailok (1448-88) was to create the position of uparaja, or heir apparent, usually held by the king’s senior son or full brother, in an attempt to regularize the succession to the throne--a particularly difficult feat for a polygamous dynasty. In practice, there was inherent conflict between king and uparaja and frequent disputed successions.