During the reign of King Chetthathirat, Okya Kalahom Suriyawong maintained a strategic alliance with
Yamada Nagamasa or Okya Senaphimuk, the influential leader of the Japanese mercenaries. Following Chetthathirat's ascension, the King's brother, Phra Sisin, sought refuge in the
monkhood. According to the Royal Chronicles, he was later lured back to the palace, stripped of his monastic robes, and arrested. He was exiled to
Phetchaburi to be executed by starvation in a deep well. However, he was reportedly saved by local monks who substituted a corpse in his place, allowing Phra Sisin to organize a short-lived rebellion. Okya Kalahom dispatched Yamada Nagamasa to suppress the uprising; Phra Sisin was eventually captured and executed in
Ayutthaya. in 1897. With his primary rival eliminated, Okya Kalahom's influence grew unchecked. In 1629, the death of his father became a pivotal political turning point. He organized a grand funeral with ceremonies and cremations normally reserved for royalty, a move seen by many as a direct challenge to the throne. When King Chetthathirat discovered that the majority of his nobles had attended the funeral instead of his royal audience, he was reportedly incensed and threatened punishment. Guided by his ally, the Okya Phraklang (Minister of Trade), Okya Kalahom launched a preemptive strike, leading his private army into the palace. King Chetthathirat fled but was captured and subsequently executed. In his place, Okya Kalahom installed the King's seven-year-old (some sources say eleven) brother,
Athittayawong, as a
puppet ruler. Acting as regent, Okya Kalahom assumed near-absolute authority, effectively setting the stage for his own coronation shortly thereafter. ==Coup and rebellion==