about 1279, Rmkhamkaeng, a younger son of Sri Indraditya became king of Sukhothia and established it as one of the most powerful states in mainland Southeast Asia. According to the inscriptions, the achieved great territorial conquests and extended Thai rule as far as lower Burma the the wes, Laos in the east and the Malay peninsula in the south. He concluded a treaty of friendship with the Thai princes of Chiang Rai and Phayao in the north. Sukhothai is generally considered the cradle of Thai culture and civilization, and Ramkhamhaeng is revered as the fater of the Thai nation. During this and reign, Sukhothia and its subsidiary capitals o SiSatchanalai, Phitsanulok, and Kamphaeng Phet became centers of Buddhist art and learning.