If you are not already in Chiang Mai, the first thing you need to do is to make your way into Chiang Mai. You can either choose to fly from wherever you are into Chiang Mai International Airport (there are daily flight connecting Chiang Mai to other popular cities in the country such as Bangkok, Phuket, and Krabi), take a bus, travel via train, or choose any other option that may seem interesting to you (road trip or hitchhike?!). Once you are in Chiang Mai, there are several options to reach the park from here.
• Take one of the many red vans lined across Chang Pauk Gate (the ones near Tha Pae Gate and Chiang Mai gate will always be costlier) which normally charge 100 baht for a round trip along with a 2 hour wait time. This works only when you take the van on a sharing basis. If you are in a large group or want the van to yourself, the drivers can ask as much as 500 Baht or more. You ALWAYS need to negotiate!
• You can rent a bicycle if you are THAT fit and energetic. It’s a steep ride up so bear in mind that it can be rally tough and exhausting unless you are used to some sort of physical activity. But, once you are at the top, it is totally worth it.
The summit of Doi Pui is around 25 km by road. From the center of Chiang Mai get on Highway 1004 also known as the Doi Suthep Road, from the northwest corner of the city moat. After around 2.2 km, zero the trip meter at the Highway 121 (also known as the Canal Road) intersection. From here follow the wide, winding mountain road past the very touristic Doi Suthep Temple at 12.3 km to Buphing Palace at 17.2 km. From here the road narrows considerably. At 18.0 a narrow lane, grandly referred to as Highway 4038, branches right toward the Doi Pui campsite at 22.0 km. This last 4 km of narrow winding lane is the main evergreen forest for birding. After the campsite at 22.0 km it is possible to follow a paved road to a Hmong village, and from there, by 4x4 vehicle only, return down the other side of the mountain to the back of Huay Tueng Tao. Even with a 4x4 this back mountain road is not recommend in the wet season. This would form a loop back to Chiang Mai and is popular with mountain bikers.
Note that the road in the up-direction from Chiang Mai can be closed in the late evening as the police usually set up a road block near the zoo preventing drunks and other undesirables ascending the mountain after dark. (Info credit: North Thailand Birding)