List of Thai monarchs

The modern order of succession of Thai monarchs begins with king Si Inthrathit who established the Sukhothai Kingdom in 1238, which is considered to be the first contemporary Tai-ethnic kingdom; it was ruled by Phra Ruang dynasty. Composing of 8 dynasties: Phra Ruang, Uthong, Suphannaphum, Sukhothai, Prasat Thong, Ban Phlu Luang, Thonburi, and Chakri. With brief interruptions, 55 monarchs and 27 viceroys have ruled over four successive kingdoms, the current monarch being Vajiralongkorn (Rama X) of the Chakri dynasty.

The modern perception is that there has been four distinct eras of Thai history, namely: Sukhothai, Ayutthaya, Thonburi, and Rattanakosin. However, the compilations of historical narratives from the old capital (pongsawadan krung kao) and the historical narratives from the king in the temple compiled by Prince Tisavarakumara, the Prince Damrong Rajanubhab, along with the Chronicles of Northern Kingdom's Histories included the Pre-Sukhothai and Pre-Ayutthaya monarchs as well. This means that the Sukhothai-Si Satchanalai city-states and the Siam Confederation and their monarchs is a part of the historical cannon as well.

Prior to the establishment of Sukhothai, Siam was a group of petty kingdoms shifting zones of influences and mandalas through wars and political marriages. Because of this, there are kingdoms and polities which existence may overlap, hence the monarchs' reigns will also overlap or even reign two polities at once. An example are Sukhothai and Ayutthaya. Ayutthaya, in the modern sense, was established during the reign of Maha Thammaracha I of Sukhothai in 1351 in which king Uthong V & Ramathibodi I (same person with two regnal names) inherited all of the confederation's polities – uniting them, hence the reign of Ayutthaya's monarchs overlaps with 4 monarchs of Sukhothai. An example for a monarch reigning multiple polities is when king Phanom Thale Sri who reigned both the Siam Confederation and the Sukhothai-Si Satchanai city-states (together 5 different polities) at the same time in 1155, while these polities were ran separately and equal to one another unlike the vassalage system in which a state is subservient to another.

The traditional accounts of the list starts with king Phra Pathomsuriya Thephanarathai Suwannabophit as the first king of all of Siam in 757 CE. He was the first king to unite petty kingdoms under one monarch. His descendants are of the Guruwamsa/Pathomsuriyawong dynasty, which is also the ancestors to most of the reigning dynasty of Sukhothai and Ayutthaya. In which, according to the traditional accounts, king Uthong V, the first king of Ayutthaya is canonically considered to be the 27th monarch of Siam. The number of monarchs up to today would total to 101 monarchs.