Froggie Went A Sailing by Sam Burns

Jasper Ferguson Conrad, much to everyone’s consternation, is the crown prince. He wasn’t raised to be king, and no one is sure if he’s up to the task, including himself. He certainly doesn’t want to be the kind of demanding, arrogant king his father has always been.
When a witch turns him into a frog and he finds himself on the run, he has to count on a near stranger—a man he may have wronged in a fit of pique—to protect him from a huge, frightening world.

He needs to break the curse and find his way home, but who can he truly trust to help him get back where he belongs, especially when his own future subjects may be plotting his death?