Loi Krathong (also written as Loy Krathong or Loy Gratong, Thai: ลอยกระทง, IPA: [lɔːj kràʔ tʰoŋ]) is a festival celebrated annually throughout Thailand and certain parts of Laos and Burma (in the Shan State). The name means roughly “Floating Crown”, and comes from the tradition of making crowns which are then floated on a river
Loi Krathong takes place on the evening of 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’, while krathong refers to a usually lotus-shaped container which floats on the water. The traditional krathong are made of the layers of the trunk of a banana tree or a spider lilyplant. Modern krathongs are more often made ofbread or styrofoam. A bread krathong will disintegrate after a few days and can be eaten by fish. Banana stalk krathong are also biodegradable, but styrofoam krathongs are sometimes banned, as they pollute the rivers and may take years to decompose. A krathong is decorated with elaborately-folded banana leaves, incense sticks, and a candle. A small coin is sometimes included as an offering to the river spirits. On the night of the full moon, Thais launch their krathong on a river, canal or a pond, making a wish as they do so. The festival may originate from an ancient ritual paying respect to the water spirits.
Government offices, corporations and other organizations big large decorated krathongs. There are competitions for the best such krathong. A beauty contest is a regular feature and fireworks have become common in recent years.
Loi Krathong is often claimed to have been begun in the Sukhothai by a court lady named Nopphamat. However, it is now known that the Nopphamat tale comes from a poem written in the early Bangkok period.is .[1] According to H.M. King Rama IV, writing in 1863, it was a Brahmanicalfestival that adapted by Thai Buddhists in Thailand to honor Buddha, Prince Siddhartha Gautama. The candle venerates the Buddha with light, while the krathong’s floating symbolizes letting go of all one’s hatred, anger, and defilements. People sometime cut their fingernails or hair and placed the clippings on the krathong as a symbol of letting go of negative thoughts. However, many ordinary Thai use the krathong to thank the Goddess of Water, Phra Mae Khongkha (Thai: พระแม่คงคา).
wikipedia.com
A lovely festival, which, in suburban Bangkok is a nightmare of crowds, pushing and shoving. The below pics were taken in Banjasiri Park, next to Emporium Shopping Centre on Sukhumvit Road, but even that was pretty crowded.
One time I took the skytrain to Saphan Taxsin, which was so crowded that he had to hire a boat, at an exorbitant price to get to the middle of the river to ‘float our krathong’.
Always Restless Feet 
What a beautiful idea – wish they’d ditch the styrofoam though! The last photo is extraordinary, so many of them! It must have been a wonderful sight seeing them all floating on the river.
Tell me about it! I think every year they produce tonnes of garbage, it’s a real shame. Quite a few schools try and educate their students about the benefit of using biodegradable materials.
But the general public prefer the cheaper option, unfortunately.