The emerging Kingdom of Ayutthaya is growing powerful.

Relations between the Ayutthaya and Lan Na had worsened since the Ayutthayan support of Thau Choi's rebellion In 1451, Yuttitthira, a noble of the Kingdom of Sukhothai who has conflicts with Borommatrailokkanat of Ayutthaya, gives himself to Tilokaraj.

Yuttitthira urges Borommatrailokkanat to invade Phitsanulok, igniting the Ayutthaya-Lan Na War over the Upper Chao Phraya valley (the Kingdom of Sukhothai).