People releasing lanterns into the night sky during the festival of light Yi Peng in Chiang Mai, Thailand. The festival is held on the full moon of the Thai calendar's 12th lunar month. Releasing lanterns symbolizes letting go all of ills and misfortunes in the previous year. Thai people believe that when the rivers are filled to their fullest and the moon is at its brightest – is the perfect time to ‘make merit’ and make a wish for good fortune in the new year.