Prince Thianracha (พระเฑียรราชา) was a son of Ramathibodi II. His half-brother Prince Chairachathirat, which had been crowned King of Ayutthaya in 1534, elevated Thianracha to Uparaja, but did not confer on him the title of King of Sukhothai. Thianracha joined his brother in the campaigns against Lanna and, in 1546, led the siege of Chiang Mai.
Chairacha died in 1546 and his son (and Thianracha's nephew) Phra Kaewfa succeeded to the throne as King Yodfa, with his mother Si Suda Chan as regent. She had Yodfa killed in 1548 and eventually put her paramour on the throne as Khun Worawongsathirat. Before doing so however, Thianracha was her co-regent, but wishing to remain faithful to his wife Sri Suriyothai, he became a monk to the Queen Mother's amorous advances.
"A band of brothers", retired officers, led by Khun Piren staged a counter-coup, killing Worawongsathirat and Si Suda Chan. Phiren Thorathep then elevated Prince Thianracha to the throne as Phra Maha Chakkraphat.
Maha Chakkraphat appointed Phiren Thorathep to the position of King of Phitsanulok as Maha Thammarachathirat, and gave him in marriage his daughter Sawatdirat. (Maha Chakkraphat passed over tradition by elevating Phiren Thorathep instead of one of his sons; but he, when still Prince Thianracha, had himself never been titular ruler of Phitsanulok.) Khun Inthrathep was rewarded with the regency of Nakhon Si Thammarat.
Upon Maha Chakkraphat's ascension, King Tabinshweti of the Burmese Dynasty of Toungoo marched to Ayutthaya, trying to take advantage of the upheavals in the Siamese capital.
The Burmese armies stopped near Ayutthaya. Tabinshweti came with his best general, the Uparaja Bayinnaung, Viceroy of Prome and Governor of Bassein. Maha Chakkraphat also took to the battleground his whole family, including Sri Suriyothai, the Uparaja Prince Ramesuan, and Prince Mahinthrathirat. At Pukaothong field, Maha Chakkraphat fought the Elephant Battle (Yuttahadhi) against the Viceroy of Prome but his elephant was overcame and ran away. Sri Suriyothai then rushed to rescue her husband but was slashed to death by the viceroy. The two princes then forced the viceroy to retreat.
The Siamese then put a culverin on a barge and sailed along the Chao Phraya to fire the enemies. The mission worked, the Burmese armies retreated but later they ambushed at Kamphaeng Phet the Siamese troops led by Prince Ramesuan and Maha Thammarachathirat. The Burmese held the two in captivity until Maha Chakkraphat gave up two male war elephants in exchange for his son and Maha Thammarachathirat.
After the war of 1548, Maha Chakkraphat insisted on battling Burmese armies near Ayutthaya, so he heavily fortified the city and de-fortified three nearby cities, Suphanburi, Lopburi and Nakhon Nayok in order to prevent the Burmese from taking them as bases. The census was taken to derive all available manpower for war. Wild elephants (especially white elephants) were caught and accumulated in the full-scale preparation for war.
Bayinnaung became King after the death of Tabinshwehti, and upon hearing about the white elephants, requested two. As Maha Chakkraphat refused, the Burmese King marched to Ayutthaya with a large army. His route was via the northern provinces since he had conquered the Lanna in 1558 and occupied Chiang Mai. Phraya Sukhothai and Phra Maha Thammaracha surrendered when Sukhothai and Phitsanulok were captured. The governors of Sawankhalok and Phichai submitted without resisting. At Chainat, Bayinnaung clashed with Prince Ramesuan's army but was able to break through. The Burmese army then reached Ayutthaya and laid siege, bombarding the city so immensely that Maha Chakkraphat "agreed to come to friendly relations with His Majesty of Hongsawadi." Additionally, he paid tribute of four white elephants and Phra Ramesuan, Phraya Chakri and Phra Songkhram were brought back to Pegu as hostages.
At Pegu, King Maha Chakkraphat entered the monkhood. Though Damrong Rajanubhab asserts the king only entered the monastery after his daughter Phra Thepkasattri was kidnapped by the Burmese, giving up his throne in dishonor. He resumed his regal powers at the urging of his son Mahinthrathirat.
In early 1568, the captive king successfully convinced Bayinnaung to allow him to go back to Ayutthaya on pilgrimage. Upon his arrival, in May 1568, he disrobed and revolted. He also entered into an alliance with King Setthathirath of Lan Xang. He was not able to convince Maha Thammarachathirat of Phitsanulok to join him and his son in the revolt. Thammarachathirat remained loyal to Bayinnaung and survived the siege by Ayutthaya and Lan Xang forces until October when the relief forces from Pegu arrived. The invasion armies laid the Third Siege of Ayutthaya in December 1568. According to Wyatt, Maha Chakkraphat died one month into the siege in January 1569. According to Prince Damrong, he died sometime during the siege. The Burmese chronicles say that the king died on 15 April 1569.