Loi Krathong is held on the full moon of the 12th month in the traditional Thai lunar calendar. In the western calendar this usually falls in November.
"Loi" means "to float" and a "Krathong" is a raft, about a hand span in diameter, traditionally made from a section of banana tree trunk. A raft has been developed to be made of bread or sometimes made of styrofoam. The reason for using bread is to protect the environment,since having many rafts in the river can create a huge water pollution problem. Bread will eventually become food for fish and other animals in the river. Even though banana leaves are biodegradable, it takes longer to be degraded than a bread. Therefore, bread is the most environmental friendly choice to make a raft whereas foam is not recommended at all. A raft is decorated with elaborately-folded banana leaves, flowers, candles, incense sticks etc..
During the night of the full moon, many people will float a small rafts (Krathong) on a river or other body of water, such as canals, lakes and seas. Some people even float a raft in a basin in their own yard. Thai people believe that floating a raft on the river is to honor and pay respect to the goddess of water. Also, floating a raft in the river is to apologize to the Goddess of the Water for the bad things we have done to the river during the past year. That is why Loi Krathong festival is held at the end of the year. Governmental offices, corporations and other organizations usually create big decorated rafts. There are also local and officially organised raft competitions, regarding its beauty and craftsmanship. In addition, there are also fireworks and beauty contests during the celebration of the festival.
The origins of Loi Krathong are stated to be in Sukhothai, but recently scholars have argued that it is in fact an invention from the Bangkok period . According to the writings of H.M. King Rama IV in 1863, the originally Brahmanical festival was adapted by Buddhists in Thailand as a ceremony to honour the original Buddha, Siddhartha Guatama. Apart from venerating the Buddha with light (the candle on the raft), the act of floating away the candle raft is symbolic of letting go of all one's grudges, anger and defilements, so that one can start life afresh on a better foot. People will also cut their fingernails and hair and add them to the raft as a symbol of letting go of the bad parts of oneself. Many Thai believe that floating a raft will bring good luck, and they do it to honor and thank the Goddess of Water, Phra Mae Khongkha (Thai: พระแม่คงคา).
Thousands of Khom Fai in Mae Cho, Chiang Mai
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 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. 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, the ancient capital of the former Lanna kingdom, where now both Loi Krathong and Yi Peng are celebrated at the same time resulting in and lights floating on the waters, and lights hanging from trees and 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.