Bang Fai Phaya Nark (Naga fireballs) is a phenomenon that the mysterious fireballs rise from the Mekong river into the air above water surface. The fireballs are smoke-less, smell-less, and sound-less. They rise 20-30 meters straight up to the air then disappear without falling back to the earth as the normal fireballs do. Their sizes vary from a thumb-size to an egg-size. The amount of the fireballs also vary, starting from around 6.00 p.m. to 8.00 or 9.00 p.m. The locations for spotting the fireball phenomenon in the Mekong River are the area of Phon Phisai, Pak Khad , Sung Kom, Sri Chiang Mai, and Bung Kan districts in Nong Khai province. The fireballs can also be found in other locations such as ponds and streams near Mekong River.
The fireball event is an unexplained phenomenon that generally takes place on the full moon night of the 11th lunar month, which also coincides with the end of the Buddhist Lent. If there are two 8th months in a particular year, the phenomenon will take place on the first waning moon night of the 11th month, which coincides with Lao's Buddhist Lent. (Panida 2538 B.E.:77)