Borommarachathirat II

Borommarachathirat II, or Borom Rachathirat II (Thai: บรมราชาธิราชที่ ๒), also known as King Samphraya (Thai: เจ้าสามพระยา) (1386–1448), was a monarch of the Ayutthaya Kingdom who reigned in the early 15th century. He is noted in Thai historiography for his roles in administration and warfare, and is associated with a period of heightened Ayutthayan activity in mainland Southeast Asia. During his reign, Ayutthaya conducted campaigns against the Lanna Kingdom and Khmer polities, and later traditions link his rule to the capture and looting of Angkor in 1431. He also appears in accounts concerning the consolidation of royal authority and the management of the kingdom's political and military affairs.

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).

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 Samphraya. In 1433, Samphraya 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.^[1]: 29

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 high reverence of Thai kingship as a deity, known as Devaraja, came from Cambodia.

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.^[1]: 31 When the last king of Sukhothai died in 1446, his grandson inherited the kingdom, further strengthening Ayutthaya control over Sukhothai.

In 1442, Chao Sam Phraya led his armies to conquer Lanna. He managed to sack the capital Chiang Mai but was unable to conquer the kingdom.

Chao Sam Phraya died in 1448 and was succeeded by his son Prince Ramesuan as Trilokanat.^[1]: 31