Yes, it is rectal prolapse.
you need to place a frog in honey bath to reduce swelling, it should go in on its own.

warm water, level no higher then frogs chin, add a few drops of honey, mix, put frog in for about 20 min. After that new water bath, this time with pedialyte (10 parts of water, 1 pedialyte) keep frog in a hospital set up for a few days for an observation.

That a beautiful frog! It would be helpful if you answer questions to trouble in the enclosure to figure out what triggered this, to avoid it in a future. Good luck.