Several unofficial yet popular Thai and international holidays like Loi Krathong festival, Chinese New Year, Chrismas, Chanuka and more are also widely celebrated in Thailand.

Even though, the western Gregorian calendar is the official calendar in the kingdom of Thailand, the traditional lunar calendar is very much in use for determining many Thai holidays, especially Buddhists. Thai ancient lunar calendar distinguishes itself from Islamic and other lunar calendars by being set up based on the yearly agricultural cycle, as it was the most important aspect of the primarily agrarian society. Thai ancient lunar calendar is divided into 12 lunar months, like the western calendar, but the months are determined by the phases of the moon, rather than by a position of the earth in relation to sun. Being based on the cycles of the moon phases, half of the lunar months are 28 days long and another half are 29 days long. The Thai lunar month is also divided into four weeks.