Phu Soi Dao National Park (or อุทยานแห่งชาติภูสอยดาว in Thai) is located in Phitsanulok and Uttaradit Provinces in northern Thailand. Res, my ex-colleague invited me to go there. I did not realize that it was a trekking trip, so I did not prepare myself much. We had about 20 people in our groups. I did not know