Make sure you use two mattresses.
lodging
You can stay at the chalet RM80; max 2 persons or at the dorm RM20 per person at the Park HQ. Both the chalet and dorm are comfortable. Of course, the only complaint is the mosquitoes, so you'd better bring your insect repellent along. At the time of writing September 2011 dorm mattresses are infested with flees. Anti-histamines can help with itching from their bites.
camping
The Park provides camping equipment at RM20 per person and your guide will help you set up camp.