This extraordinary miracle always occurs at the beginning of the full moon night in the eleventh lunar month (End of Buddhist Lent). It can be seen along the Mekong River in the districts of Mueang, Phon Phisai, Pak Khat, Bung Kan, Tha Bo, Si Chiang Mai and Sangkhom.

Bang Fai Phaya Nak is a term used for red and pinkish fire balls, which according to belief, belong to Phaya Nak or the great serpent of the underwater world. On the day marking the End of Buddhist Lent, a great number of people come to witness this phenomenon.