Wan Ok Phansa (Thai: วันออกพรรษา, pronounced [wān ʔɔ̀ːk pʰān.sǎː]; literally "day of going out of Vassa", ออก in Thai meaning exit or leave) is the last day of the Thai-Lao observance of Vassa. 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. 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 as a way to please the Nāga spirits. Along the Mekong River, people launch little hot air balloons, acting as lanterns, around the night of Wan Ok Phansa.

Launching the boats (or the lanterns) symbolizes one's wishes but also getting rid of unnecessary negative feelings.

Etymology

"Wan" (Thai: วัน) means "day",^[2] "Ok" (Thai: ออก) means "to exit; to leave",^[3] and Phansa (Thai: พรรษา) is the Thai word for Vassa.

Dates for Wan Ok Phansa