Mahathammaracha I (r. 1346–1368) was a Sukhothai king known as a great scholar and patron of Buddhism who even became a monk for a brief period of four months. A treatise on Buddhist cosmology, the "Tribhumikatha" ("Trai Phum Phra Ruang", "The Three Worlds according to King Ruang"), has been attributed to him. The "Trai Phum Phra Ruang" is one of the oldest traditional works of Thai literature. During the reign of Mahathammaracha I, another group of monks arrived from Sri Lanka, led by Somdet Phra Mahasami (Sumana), who was associated with a Sri Lankan forest monastery named Udumbaragiri.