Maha Thammaracha I
Maha Thammaracha I (, ), born as Li Thai (, ), was a king of the Sukhothai Kingdom, and the first Buddhist philosopher to write in the Thai language. He reigned from roughly 1347 until his death in 1368. Li Thai was the son of Loe Thai and the grandson of Ram Khamhaeng the Great. The exact chronology of Li Thai's rise to the throne is unclear. Popular tradition names him as the fourth king of Sukhothai, but dynastic records seem to indicate that at least one other king (Ngua Nam Thum) ruled between Li Thai and his father, as  well as the regent Phaya Sai Songkhram who ruled during Loe Thai's absence following the death of Ram Khamhaeng. Li Thai served as Upparat (viceroy) during his father's reign from the city of Si Satchanalai, an important urban center of the early Sukhothai Kingdom. Li Thai wrote the "Traiphum Phra Ruang" ("three worlds by Phra Ruang", Phra Ruang being the dynastic name of Li Thai's lineage), a religious and philosophical text describing the various worlds of Buddhist cosmology, and the way in which karma consigns living beings to one world or another. The Ten Virtues of a  sovereign were set down as guiding principles for Thai monarchs. The "Traiphum Phra Ruang" would go on to serve as an important political document, being re-interpreted in response to changes in the domestic and international political scene. Li Thai also built Wat Phra Si Rattana Mahathat in Phitsanulok, including Phra Phutta Chinnarat, the biggest Buddha image in the northern territory of Siam. According to George Cœdès, Li Thai's devotion to Buddhism and his religious works earned him the title Maha Thammaracha, meaning "great pious king". He constructed many Buddha footprints and restored Wat Mahathat of Sukhothai. He was  succeeded by his son Lue Thai.