The majority of people, locals and foreigners alike, who visit Kulen Mountain do so as a day trip from Siem Reap. You can drive to the top or hike from the foot of the mountain in about 2 hours. The hike does give you the option to see a couple of things en-route that you may otherwise miss such as:
Elephant statues - symbols of Hinduism stands at the foot of Mount Kulen.
Preah Ang Jub - is reached via muddy tracks, obstacles such as fallen trees and roots and challenging steps. It has a pool of sacred water whose source is at the top of the mountain. Buddha devotees offer prayers here.
On our day trip, due to limited time we skipped the hike. Instead we drove straight up the mountain to the car park. From this point you can either walk or drive (or a combination of the two) between the different things there are to see and do.
Preah Ang Thom and the Reclining Buddha