Si Saowaphak (Thai: ศรีเสาวภาคย์, pronounced [sǐː sǎw.wā.pʰâːk]) or Sanphet IV (Thai: สรรเพชญ์ที่ ๔; r. 1610/11–1611[3]) was a short-reigning king of Ayutthaya of the Sukhothai dynasty in 1610/11.

[4]: 203 When Ekathotsarot died in 1610/11, Prince Si Saowaphak succeeded his father on the throne.

In the same year the Japanese traders entered the palace, and held Si Saowaphak hostage until he vowed not to hurt any Japanese people.

The Japanese then took the Sankharat (Supreme Patriarch) hostage to the mouth of Chao Phraya where they left for Japan.

This biography of a member of a Thai royal house is a stub.