Ranong has lots of hot-springs. I passed 4 just driving around the place. This isn't even the best of them, it's just the first I explored.
The water from this hot-spring is piped into pools to bathe in, and you can enjoy the natural warm soothing mineral waters that way. However this spring is not that hot, it's just warm, and it's not much different from sitting in a warm bath. The hot-spring itself isn't why people really come here and the pools are mostly empty.
No, the big attraction for this Pornrang is the fish.
Next to it, runs a river, and in the river are many hungry fish. You put your feet into the water and get a fish pedicure. This is not like the fish pedicures in some shopping malls, not small fish nipping delicately at your toes. No these are real fish, small to big. Some bigger than piranha size. You can feel their teeth as they try to bite off your a limb.
I exaggerate a little, but a few times, I had to take my feet out of the river it was too too much. A weir splits the river in two with the big fish in the upper portion. Count your toes before and after the dip just to make sure.
In hindsight I should have worn a less revealing swimming costume, this is the muslim south of Thailand and there were a lot of eyes on me, a little more modesty would be better.