There are porters (both men and women) who will carry your "stuff" up and down Phu Kradung for 10 B per kilogram. Believe me, it is worth it. We combined what we needed, had 19 kg. going up and 16 kg. going down. The porter does not go with you, so you will need to carry any necessities yourself.
Maybe the Forest Service and VIP guests can use helicopters, but otherwise you must climb/walk up and down Phu Kradung, unless you want to pay to be carried up by porters. It was 5.4 km from Park Headquarters to the mountain top (1288 m) with a change in elevation of 1200 m and then another 3.8 km of flat walking to the Visitors' Center. At the really steep cliffs, they have stairways. In many places there are stone steps. People in good shape can do the climb in ~3 hrs. It took me 5.5 hrs going up and 4 hrs. coming down (counting the rest stops). By the way, the Forest Service staff get to use motorized vehicles (motorcycles, trucks, etc.) to get around on top; however, porters and visitors must walk. I don't know if motorized vehicles are banned from the undeveloped "green forest" area.