Asarnha Bucha Day, one of the most sacred days in Buddhism, is observed on the 15th Day of the Waxing Moon in the Eight Lunar Month to commemorate the day on which Lord Buddha delivered his first Sermon, or Dhammachakkappavattanasutr, before the first five disciples in Buddhism. The day also marks the beginning of the worship of the Triple Gem, namely: the Lord Buddha, His Teachings and His Disciples.

In his First Sermon, Lord Buddha taught the Middle Way or, Majjimapatipada, and how to reach Nirvana, and as a result one of the five ascetics who was named Kondanya, attained enlightenment. In recognition Thailand was the first Buddhist country to recognise the importance of the day, as a sacred and national holiday.