Prabat Somdet Phra Sanpet III or Somdet Phra Ekatotsarot is the King of Ayutthaya from 1605 to 1610 succeeding his brother Naresuan.

His reign is mostly peaceful as Siam is at this time a powerful state through the conquests of Naresuan.

Also during his reign, foreigners of various origin begin to fill the mercenary corps.