Pha Dong Ko (ผาดงก่อ), pronounced pah dohng gaw, offers some of the best views from atop the Phu Phan Mountain range, providing beautiful views across Sakon Nakhon into neighboring Udon Thani and Kalasin province. It is also one of the best places in Sakon Nakhon to watch the sunrise.
Pha Dong Ko (aka The Forest Cliff) is 622 meters above sea level, and the highest peak of the Phu Phan Mountains. The viewpoint has a Buddhist style observatory platform to get an enhanced view of the Thai countryside below, which looks like a beautiful patchwork quilt. Known as Song Dao Tower (หอส่องดาว), this platform is also a beautiful place to stargaze and watch meteor showers in Thailand.
Pha Dong Ko viewpoint is only about 1 kilometer away from Phu Pha Lek National Park, and 1.5 km from Wat Tham Apai Damrongtham and sacred pagodas such as Phra Chedi Wihan Pariniphan, which also offer gorgeous views. The best (clearest) views are during the cool season (December - February). However, if you go during the rainy season, you'll also be able to visit the nearby Kaeng Kula Waterfall (น้ำตกแก่งกุลา), which has 9 tiers.
Pha Dong Ko has a nature trail which you can hike on, and if it is a cool day the back road down the mountain that leads directly to the famous row of pagodas/chedis makes for a lovely walk. You are likely not going to see any cars on the small road, and indeed the viewpoint itself is often solitary (except on weekends), making it a lovely place to relax and meditate upon life.
Pha Dong Ko (ผาดงก่อ) is about a 1 hour and 45 minute drive from Sakon Nakhon city and a 1.5 hour drive from downtown Udon Thani. If you enjoy birding, then do head over to the main entrance of Phu Phan National Park, which is one of the best bird watching spots in Thailand.