In an effort to decrease the multitude of threads about these events, we ask that all questions about the events be added to this thread rather than starting new threads or reviving old ones.
There are four separate events that take place during or around the 12th full moon of the Thai lunar calendar (usually the full moon in November). Unfortunately much dis-information is floating around the internet causing much confusion.
Yee Ping Festival is celebrated throughout northern Thailand and originated to mark the beginning of winter. Celebrated by the use of lanterns, during the festival folks decorate their house, businesses with lanterns of various types and launch khom lois (fire lanterns) into the skies to bring them good luck.
Loi Krathong Festival is celebrated throughout all of Thailand, with the most enjoyable locations being Chiang Mai and Sukhothai. Its origination is not certain, but believed to be making an offering to the water spirits in thanks for the water that the rainy season brought before the dry season. It is marked primarily by floating krathongs, which are lotus flower shaped offerings carrying a candle, incense and a coin, down a river or on a body of water such as a lake, canal or moat.
Lanna Khatina Ceremony (aka Mae Jo "public" event) is a Buddhist ceremony conducted by the Dharma Sect and held at the Tudongkasatan Lanna (a meditation center) behind Mae Jo university. It is a long religious affair that culminates with mass launchings of thousands of khom lois. Videos of these launches are posted on YouTube and other video sharing site, often mis-labeled as Yee Ping. The ceremony is open to anyone who wishes, but tourists need to remember it IS a religious ceremony not a show and polite dress is mandatory.
Yee Ping Lanna (aka Mae Jo "tourist" event) is a made for tourists recreation of the Lanna Khatina Ceremony, which unfortunately was poorly named leading to confusion (it is NOT Yee Ping). Admission to this event is by ticket only, with only a limited number of spaces available and a $100 plus price tag. It follows the format of the religious ceremony culminating with the mass balloon launch, though not as many as the original.
Both Yee Ping Festival and Loi Krathong Festival are celebrated during the full moon, with a large variety of events planned for three days around the full moon, including parades, concerts, dancing, food festivals, etc. During the three official days of the festivals, plus often a day or two before and after, the skies over Chiang Mai are filled with hundreds, even thousands of khom lois floating upward. And the Ping River has a myriad of krathongs floating along its length, like a million twinkling stars on the water.
The Lanna Khatina Ceremony and its look alike Yee Ping Lanna take place around the same time, with Lanna Khatina often on the weekend before the full moon and the tourist event the weekend after. However these dates are not officially announced until a month or so ahead (usually in either September or October) and the dates have been known to vary from the week before/after scenario.