49.3

"Lanna (northern Thai) people use sky lanterns all year round, for celebrations and other special occasions. One very important festival in which sky lanterns are used is the Lanna festival known as "Yi Peng" (Thai: ยี่เป็ง) which is held on a full moon of the 2nd month of the Lanna calendar ("Yi" meaning "2nd" and "Peng" meaning "month" in the Lanna language). Due to a difference between the old Lanna calendar and the traditional central Thai calendar it coincides with Loi Krathong which is held on the full moon of the 12th month in the traditional Thai lunar calendar. During the Yi Peng festival, a multitude of khom loi (Thai: โคมลอย, literally: "floating lanterns") are launched into the air where they resemble large flocks of giant fluorescent jellyfish gracefully floating by through the sky. The most elaborate Yi Peng celebrations can be seen in Chiang Mai,[3] the ancient capital of the former Lanna kingdom. The festival is meant as a time for tham bun (Thai: ทำบุญ), to make merit. People usually make khom loi from a thin fabric, such as rice paper, to which a candle or fuel cell is attached. When the fuel cell is lit, the resulting hot air which is trapped inside the lantern creates enough lift for the khom loi to float up in to the sky. In addition, people will also decorate their houses, gardens and temples with khom fai (Thai: โคมไฟ): intricately shaped paper lanterns which take on different forms.
It is considered good luck to release a sky lantern, and many Thais believe they are symbolic of problems and worries floating away. In recent times, khom loi have become so popular with all Thai people that it has become an integrated in to the Loi Krathong festival in the rest of country."

taken from wikipedia