The western neighbour of the Khmer, the first Thai kingdom of Sukhothai, after repelling Angkorian hegemony, was conquered by another stronger Thai kingdom in the lower Chao Phraya Basin, Ayutthaya, in 1350. From the fourteenth century on, Ayutthaya became Angkor's rival. Angkor was besieged by the Ayutthayan king Uthong in 1352, and following its capture the next year, the Khmer monarch was replaced with successive Siamese princes. Then in 1357, the Khmer king Suryavamsa Rajadhiraja regained the throne. In 1393, the Ayutthayan king Ramesuan besieged Angkor again, capturing it the next year. Ramesuan's son ruled Khmer a short time before being assassinated. Finally, in 1431, the Khmer king Ponhea Yat abandoned Angkor as indefensible, and moved to the Phnom Penh area.