You can book a trip to the park using any number of ticket agents in Chiang Mai. I chose to walk directly to their office near Tapae Gate on Moonmuang Road. Because bookings are limited to avoid overcrowding, you simply cannot show up at the park without a pass. 2500 bahts gets you a full day pass. You can also participate in various volunteer program for a more lengthy stay. Shuttles leave every morning from Chiang Mai to take you directly to the sanctuary.