Si Saowaphak

Phrabat Somdet Phra Sanphet IV (Thai: พระบาทสมเด็จพระสรรเพชญที่ ๔) or Somdet Phra Si Saowaphak (Thai: สมเด็จพระศรีเสาวภาคย์) (- 1611) was a short-reigning king of Ayutthaya of the Sukhothai dynasty in 1610. Prince Si Saowaphak was the son of Ekatotsarot and had an elder brother Prince Suthat who was made the Uparaja in 1607 but committed suicide the same year. Prince Si Saowaphak, as his father's second son, was expected to be invested the title of Crown Prince. However, Ekathotsarot did nothing to make Si Saowaphak his successor .

When Ekathotsarot died in 1610, Prince Si Saowaphak succeeded his father on the throne. Si Saowaphak was said to be one-eyed and incompetent as he fell under the influences of the nobility. In the same year the Japanese bandits looted Ayutthaya, entered the palace, and held Si Saowaphak for a custody. Only when Si Saowaphak vowed not to hurt any Japanese people the bandits released the king but held the Sankharat (Supreme Patrairch) to the mouth of Chao Phraya where they left.

The nobility viewed Si Saowaphak as an incompetent monarch so they launched a coup deposing him in 1611 led by Suriyawong the Minister of Defence (later Prasat Thong). Si Saowaphak was then executed and the throne was given to his half-brother Prince Si Sin who was a monk.