Wan Ok Phansa
Wan Ok Phansa (Thai: วันออกพรรษา; literally "the Final Day of the Vassa") is the last day of the Thai-Lao observance of Vassa. It occurs in October, three lunar months after Wan Kao Pansa. In 2015 it will be celebrated on 27 October; in 2016 on 16 October.
The day is celebrated in Isan by illuminated boat processions (Thai: ไหลเรือไฟ lai ruea fai, Isan: ไหลเฮือไฟ lai huea fai), notably in Nakhon Phanom Province on the Mekong and in Ubon Ratchathani on the Mun River.
The main ceremonies feature boats of 8–10 metres in length, formerly made of banana wood or bamboo, but now sometimes of other materials. The boats are filled with offerings such as khao tom (glutinous rice sweets wrapped in banana leaves) and decorated on the outside with flowers, candles and lamps. The boats are launched in the evening.
Additionally, some celebrants individually launch their own, smaller vessels. Boat races also take place around this time in many places throughout the country.
The phenomenon known as the "naga fireballs", in which glowing egg-sized balls rise out of the Mekong River, is most often reported around the night of Wan Ok Phansa. A clear reason for the fireballs has yet to be determined.