Snakes and frogs are not usually friends. Snakes prey on frogs, and frogs do their best to avoid snakes. So this situation seems bizarre.
This picture shows something totally different from the norm. It shows frogs hitching a ride on the back of a snake. For all we know, the snake might be playing a fast one on the frogs. It might just be taking them to its lair, where they would not be able to escape.