The temple itself is not very interesting. It is its herbal sauna at about hundred meters on the other side of the road that made its reputation. Two small very basic rooms, one for girls and one for boys (go in the right one), showers and benches outside, a changing area with toilets and lockers, the place is not a luxurious spa. Here no effort was made for decorationor the comfort of visitors but it is normal it is managed by a temple. And the price is unbeatable ! The Wat Pho herbal sauna is certainly THE curiosity and best deal of Koh Phangan island.
You can also go to pray in the temple after the sauna to be thankful for this moment of relaxation and intense sweating of course...