"Kaeng Ah Hong" is a natural rapid in the Mekong River that is beautiful, and bound by belief and faith about the serpent; it is believed that the Kaeng Ah Hong area is the deepest point of the Mekong River, and it is the gateway connecting the human world with the underwater world which is the residence of the Naga. It is believed that; if a lemon is thrown into Kaeng Ahong, it will appear in Kham Chanod Forest, Ban Dung District, Udon Thani Province. Then, it became a belief that connects the human world with the underwater world of the Naga Kaeng Ahong area is one spot where the Naga Fireballs phenomenon occurs every day of the Buddhist Lent day on the 15th day of the 11th lunar month of every year and there are tourists, including those who have faith in the Naga, come to travel regularly throughout the year.