Dr. Kanoksilpa, a pediatrician at Nong Khai clinic, researched this phenomenon for 4 yrs and concludes the most probably clarification to get seasonal accumulations of methane gas Phaya Nak or Phaya Nāga (Thai: พญานาค; RTGS: phaya nak; lit. 'lord of Nāga', phaya derived from Mon which suggest high nobility) https://gregorynamwi.frewwebs.com/30085195/the-smart-trick-of-23naga-that-nobody-is-discussing