Asahna Bucha Day is a national holiday in Thailand celebrated annually on the full moon of the eighth month of the lunar calendar. This meaningful day in Buddhism commemorates the Buddha's first sermon in Benares, India, where he set out the doctrine that had come to him following his enlightenment. Asahna Bucha, also known as Dhamma Day, attracts the passionately devout to Buddhist temples across the country to make merit.

The day starts with people making merit in the early morning at Buddhist temples. Devotees usually bring offerings and perform rituals, such as freeing birds and fish. Later, the 'wien tien' ritual takes place, in which worshippers walk clockwise three times around the temple holding flowers, incense, and a lit candle. The three circuits are for the Buddha, the Dhamma (Buddhist teachings), and the Sangha (Buddhist community).

Another significant part of the Asahna Bucha Day is the ceremony of 'Khao Pansa'. It marks the beginning of the Buddhist Lent or the Rains Retreat. This period is a time when monks retreat to their temples for intensive meditation. Laypeople also use this time to make merit by abstaining from bad behavior, giving up indulgences, or adopting new, beneficial habits. Asahna Bucha Day, rich in symbolic tradition, supports the continuation of Buddhist teachings and practices.