yi peng - floating lantern festival

"The most elaborate Yi Peng celebration is in Chiang Mai, where thousands of people gather and launch hot-air lanterns into the night sky. Made of a thin fabric, usually rice paper, a candle or fuel cell is attached so that when it's lit, the hot air trapped inside creates enough lift for it to float away. It's a spectacular sight as thousands of lanterns are released at the same time. The festival is meant as a time to pay respect to higher deities - you say a prayer, make a wish and then watch as your lantern floats away. (Many people also believe that the lantern will carry your troubles away with it.)"

Source:  MyModernMet