Every year around the end of the Buddhist Lent, crowds gather along the Mekong River to watch the Naga fireballs — glowing balls that, according to Wikipedia, "are alleged to naturally rise from the water high into the air." They are said to be "reddish" and to "range in size from smaller sparkles up to the size of basketballs," and "the number of fireballs reported varies between tens and thousands per night." Locals attribute them to phaya nak, "a giant serpent (Nāga) said to live in the Mekong."
Skeptics have a less mystical explanation. A 2002 iTV documentary "showed Lao soldiers firing tracer rounds into the air across the river from the festival," and Thai biologist Jessada Denduangboripant analyzed footage and "concluded that the effect was caused by the firing of flare guns from the other side of the river."
Lao authorities reject that. After investigating during a 2021 COVID-19 curfew, an official stated that "it is extremely unlikely that anyone could have fired weapons or flare ammunition without our knowledge on that night."
