Prayad, 88, was a former assistant commander of the Air Force, a former president of Thai Airways International, and a senator in 1992.
Prayad was initially believed to have committed suicide, as his.38 pistol was found in his right hand. Police collected one slug from the scene.
Police will look into the death in detail before determining the cause of death, Prawut said.
Prayad’s body, with a gunshot in the right temple, was found near the temple’s crema