According to Brian Dunning of Skeptoid, one Dr. Manos Kanoksilp, a pediatrician, theorises that the Naga Fireball phenomenon requires a precise alignment of the sun, moon and Earth, and that the Makong River provides a perfect storm of conditions, regarding methane and oxygen levels combined with ambient temperature, to bring about the fireballs every year at the same time.[1] The Thai Science Ministry apparently concurs, citing an experiment headed by the ministry’s Deputy Secretary, Saksit Tridech. Tridech and his team used equipment to measure conditions during the celebration and apparently determined that the fireballs were the result of built up phosphine gas.[2] Phosphine is manufactured for industrial purposes through a defined chemical process, and it’s not clear how it is generated in nature. Though most believe, similar to methane, it is the product of bacterial reduction of phosphate in decomposing organic material.
Brian Dunning disagrees with the swamp gas theory, however. The swamp gas process described above, based on methane gas, requires highly specific conditions. The right concentrations of methane and oxygen and certain environmental conditions are necessary for spontaneous combustion. Dunning believes it’s unlikely that those conditions can be found consistently on the same date at the same place, year after year. It may come as no surprise that he favours the Laotian guards firing into the sky theory, and suggests that they may be paid to do so by local officials.
Phosphine however, is a touch more volatile than methane, and could account for the Naga Fireball phenomenon, but it too would require special circumstances to be consistent over time.