Really neat to see all the old graves. Very well taken care of. The walk to the graveyard is up hill. Also bring a ribbon to tie on the tree on the path to the graveyard. Short up hill walk.
The way up takes around 3 hours, it goes through the dense forest most of the time. The temperature goes down the higher you hike. One of the nicest hikes in Thailand.
The hike takes roughly 4 hours to go up and 3h to go down. It'd be also great to stay the night at the top to enjoy the stunning views with the sun setting and rising.