He was a son of
Intharacha, who had secured the Ayutthayan throne for the
Suphannaphum dynasty. He had two elder brothers, Prince Aiphraya and Prince Yiphraya, and was appointed by his father as governor of
Chainat (the old name of
Phitsanulok). fought each other to the death on elephants at Pa Than Bridge. The painting is now in the Warophatphiman Hall,
Bang Pa-In Royal Palace. In 1424, upon the death of Intharacha, his two older brothers marched from their respective cities to Ayutthaya to claim the throne. They engaged in single combat on elephants, during which both were killed, leaving the throne to Sam Phraya. In 1433, Sam Phraya led Siamese forces in a campaign against Cambodia—then the
post-Angkor Khmer Kingdom—and plundered
Angkor Thom. The attack contributed to the Khmers' abandonment of Angkor and the relocation of their capital further to the southeast. And he ordered the
Nakhonin to rule in Cambodia. Later, the Nakhonin died, he appointed the Prince of Phrak, his another son to reign in Cambodia. But the prince was assassinated by
Ponhea Yat. Therefore allowing Ponhea Yat to become king instead of the prince. After that, Ponhea Yat moved the capital to
Chaktomuk. To escape the influence of Siam, and wanting to move the center closer to the sea to further promote maritime trade. The conquest, however, brought in a large influx of
Khmer culture and traditions into the Siamese court. For example, the idea of the Thai king as a divine figure—the
Devaraja concept—was adopted from
Angkor. In 1442, King Sam Phraya launched a major military expedition to conquer
Lan Na during a period of succession turmoil following the death of King Sam Fang Kaen. Although the Ayutthayan forces reached and laid siege to the capital of
Chiang Mai, they were unable to capture the city or achieve a decisive victory over the newly ascended King
Tilokaraj. The campaign ended in a retreat after King Sam Phraya reportedly fell ill during the siege. King Sam Phraya also sought northward expansion. He married a daughter of the vassal Prince of
Sukhothai, Maha Tammaraja IV, and had a son, who will grow up to be Prince
Ramesuan. When the last king of Sukhothai died in 1446, his grandson inherited the kingdom, further strengthening Ayutthaya control over Sukhothai. King Sam Phraya died in 1448 and was succeeded by his son Prince Ramesuan as Trilokanat. ==Legacy==