The beautifull yi peng lantern festival

Loi Krathong coincides with the Lanna (northern Thai) festival known as "Yi Peng" (Thai: ยี่เป็ง). Due to a difference between the old Lanna calendar and the Thai calendar, Yi Peng 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). A multitude of Lanna-style sky lanterns (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 festival is meant as a time for tham bun (Thai: ทำบุญ), to make merit. People usually make khom loifrom 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 into 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. Khom thue (Thai: โคมถือ) are lanterns which are carried around hanging from a stick, khom khwaen (Thai: โคมแขวน) are the hanging lanterns, and khom pariwat (Thai: โคมปริวรรต) which are placed at temples and which revolve due to the heat of the candle inside. The most elaborate Yi Peng celebrations can be seen in Chiang Mai,^[2]the ancient capital of the former Lanna kingdom, where now both Loi Krathong and Yi Peng are celebrated at the same time resulting in lights floating on the waters, lights hanging from trees/buildings or standing on walls, and lights floating by in the sky. The tradition of Yi Peng was also adopted by certain parts of Laos during the 16th century.

Source : http://en.wikipedia.org/wiki/Loi_Krathong