Si Saowaphak , usually called as Sanphet IV, was the twenty-first sucessor of the Kingdom of Ayutthaya , today's Thailand . His reigning time had just lasted 1 year from 1610 for the death of his predecessor to 1611, when being killed by his half-brother Prince Sri Sin.
Si Saowaphak was the son of King Ekathotsarot , who had contributed to free Siam from the domain of Burmese of the Taungoo Dynasty. It was written in some source that the first successor of Ekathotsarot was the other son. However, the throne had still been assigned to Si Saowaphak.
There is few of historical sources which mention about Saowaphak's life.