Complex sentence: He then appointed his first son, Intharacha, as the new ruler of Angkor Thom, before returning to Ayutthaya with a great number of Khmer people (including royals and nobles) and valuables.
Split into simpler sentences: He then appointed his first son, Intharacha, as the new ruler of Angkor Thom. Borommarachathiat II returned to Ayutthaya with a great number of Khmer people and valuables.