After the war of 1548, Maha Chakkraphat insisted on battling Burmese armies near Ayutthaya, so he heavily fortified the city. He, however, de-fortified other cities in order to prevent the Burmese from taking them as bases. The census was taken to derive all available manpower to war. The arms and horses and elephants (white elephants) were caught and accumulated in the full-scale preparation for war.
Bayinnaung, which became King in 1551 after the death of Tabinshwehti, upon hearing about the white elephants, requested for some. As Maha Chakkraphat refused to gave them off, the Burmese King marched to Ayutthaya. Bayinnaung had conquered the whole kingdom of Lanna in 1558, with auxiliary troops from Lanna, he led a massive army into Sukhothai Kingdom. Maha Thammarachathirat then realised the greatness of Bayinnaung army and readily surrendered, giving up Phitsanulok and becoming Burmese tributary. At Chainat, Bayinnaung clashed with Prince Ramesuan's army but was able to break through.
The Burmese army reached Ayutthaya and laid siege bombarding the city so immensely that Maha Chakkraphat sued for peace in 1564. The King and Crown Prince Ramesuan were brought back to Pegu as hostages. Bayinnaung left Mahinthrathirat, one of Maha Chakkraphat's sons, as vassal king, along with a garrison of 3,000 men. At Pegu, King Maha Chakkraphat entered the monkhood.[1]