This is the stomach-churning moment a snake struggled to swallow a frog.

Swiss tourist Erich Fahrni, 52, saw the rat snake while he was cleaning trash from a river in Chonburi, Thailand, on October 15.

Footage shows the rat snake struggling to swallow its prey, which was too big. The snake then gave up and slithered away.

Erich said that the frog was lucky it was not eaten by the snake, but not lucky enough as it was already dead from the venom.

He said: "Sometimes you are lucky, but sometimes you aren't. This frog was already dead despite the snake giving up."

This is the stomach churning moment a snake struggled to swallow a frog. Swiss tourist Erich Fahrni, 52, saw the rat snake while he was cleaning trash from a river in Chonburi, Thailand, on October 15. Footage shows the rat snake struggling to swallow its prey, which was too big. The snake then gave up and slithered away. Erich said that the frog was lucky it was not eaten by the snake, but not lucky enough as it was already dead from the venom. He said: "Sometimes you are lucky, but sometimes you aren't. This frog was already dead despite the snake giving up."