The emerging Kingdom of Ayutthaya was also 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 had conflicts with Borommatrailokkanat of Ayutthaya, gave himself to Tilokaraj. Yuttitthira urged Borommatrailokkanat to invade Phitsanulok, igniting the Ayutthaya-Lan Na War over the Upper Chao Phraya valley (the Kingdom of Sukhothai). In 1460, the governor of Chaliang surrendered to Tilokaraj. Borommatrailokkanat then used a new strategy and concentrated on the wars with Lanna by moving the capital to Phitsanulok. Lan Na suffered setbacks and Tilokaraj eventually sued for peace in 1475.