Loi Krathong coincides with the Lanna (northern Thai) festival known as Yi Peng (Thai: ยี่เป็ง). Yi means "two" and peng means a "full moon day". Yi Peng refers to the full moon day in the second month according to the Lanna lunar calendar (the twelfth month according to the Thai lunar calendar).[4]
Swarms of Lanna-style sky lanterns (khom loi (Thai: โคมลอย), literally: "floating lanterns") are launched into the air where they resemble large shoals of giant fluorescent jellyfish gracefully floating through the sky.