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)
Beliefs and the Legend - Mekong River: Thai people in the northeast, especially in the provinces on Mekong riverbank, have believed for generations that Mekong River was the route of the Naga named 'Pu Chao Sri Sutho' who crawled around the mountains, differently from the other Nagas who crawled straight through the mountains. The route therefore became such winding and was called Lum Nam Kod (winding river), which then became slightly out of tone to Lum Nam Kong or 'Kong river' (Special Report 2544 B.E.: inside cover).
The Legend of Bang Fai Phaya Nark: When the Lord Buddha was in his Bodhisatta Phaya Kan Kark incarnation, he incarnated in Sida's belly. When he grew up and practices his pray, Lord Indra made him a very good-looking person and also gave Udorn Kurutaweeb to be his wife. The couple regularly studied Dhama and gave sermon to all kinds of beings.
Both human and other beings admired and greatly had faith on the sermons of Lord Bodhisatta Phaya Kan Kark. They then forgot to dedicate offerings to Phaya Tan, the God who created the beings and rainfall for the earth.
Phaya Tan then became very angry because he did not receive any offerings from human and beings.Moreover, all the angels who are usually around him had gone to attend the sermon performed by Phaya Kan Kark.
The angry Phaya Tan then condemned all of the beings by not making any rainfall for the total period of seven years, seven months, and seven days. The drought then spread to the whole earth. Human beings then urged to Lord Bodhisatta and asked for his help.
Phaya Kan Kark then realized, by his sight, and told the human that Phaya Tan did not receive offerings and became angry, hence resulting in not making rainfall for seven years. When Phaya Nagi, a mythical serpent and the king of the underworld, who was attending the sermon knew the cause, he then took his troops to attack Phaya Tan who lived in heaven, despite the advice against from Lord Bodhisatta Phaya Kan Kark.
But Phaya Nagi lost to Phaya Tan and was heavily wounded. Lord Bodhisatta Phaya Kan Kark felt sympathize and he considered that Phaya Nagi did all for the happiness of mankind. He then blessed Phaya Nagi and the followers.
'May your wound gets fully cured and becomes beautiful pattern as if crystal scales. Your crest shall become beautiful silvery crystal. Your pain shall be wholly eliminated. You shall be happy and become a truly representative of such a happy place' (Copied from a performance script and adapted to be Thai dialogue as spoken in central region).
Since then, Phaya Nagi dedicated himself as a servant to Lord Bodhisatta in every reincarnation. However, the drought remained. Lord Bodhisatta Phaya Kan Kark planned to attack the heaven. The termite king built an anthill to reach the heaven. Kings of Mang Ngod, Mang Ngao (king scorpion) transformed themselves and catch on Phaya Tan's clothes. Phaya Nagi transformed himself as a small centipede and hid in Phaya Tan's shoe. When Lord Bodhisatta Phaya Kan Kark gave the signal, all of them bit and poisoned Phaya Tan.
Phaya Tan then lost and begged Lord Bodhisatta Phaya Kan Kark to release him. Lord Bodhisatta Phaya Kan Kark asked Phaya Tan to give three blesses in return, which are:
One…Let the rainfall become regular in each season, and the mankind shall offer the fireballs as a propitiation for Phaya Tan.
Two…After the rain, there must be frogs available in the paddy field.
Three…When it reaches the harvest season, Phaya Kan Kark shall give signal that the rice or farming products are truly rich.
When Phaya Tan heard so, he agreed to grant these three blesses. Since then, at the middle of the sixth month, the northeasterners make the streak fireballs, parade them around the village, and fire them to worship Phaya Tan.
When the Lord Buddha had enlightened, he traveled to propagate Buddhism around the Indian subcontinent. Phaya Nagi who followed him as a servant knew by his sight that the Lord Buddha was previously Phaya Kan Kark. He then transformed himself as a human and asked for becoming a Buddhist monk.
In one night, Phaya Nagi was asleep and mistakenly returned to his original figure. All the monks were frightened. When the Lord Buddha knew what happened, he asked Phaya Nagi to give up the monkshood because the beast is not allowed to be a Buddhist monk.
Phaya Nagi accepted the Lord Buddha's request, but he asked in return that all the persons who wish to become Buddhist monk must be called 'Nagi,' for the pride of Phaya Nagi, before they enter the Buddhist monastery. Since then, the persons who are going to be a monk is called 'Naga'.
Later on, the Lord Buddha traveled to perform a sermon, during the Buddhist Lent, in the second heaven for Buddha mothers and the angels. When the Buddhist Lent ended, Phaya Nagi and his followers prepared offerings and performed fireballs for the Lord Buddha as he returned to the earth.
Since then, on the full moon night of 11th lunar month, there has been phenomenon that the fireballs raise from Mekong up to the air until present. People call this natural phenomenon 'Bang Fai Phaya Nark'.