It occurs in October, three lunar months after the beginning of Vassa, known as Wan Khao Phansa (Thai: วันเข้าพรรษา).
[1] The day is celebrated in the Isan province by illuminated boat processions (Thai: ไหลเรือไฟ lai ruea fai [lǎj rɯ̄a fāj], Northeastern Thai: ไหลเฮือไฟ lai huea fai [lǎj hɯ́a fáj]), notably in Nakhon Phanom Province on the Mekong and in Ubon Ratchathani city 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.
Along the Mekong River, people launch little hot air balloons, acting as lanterns, around the night of Wan Ok Phansa.