Asalha Puja, or the celebration of the First Sermon of Buddha, is one of the most important religious celebrations in Thailand, a country steeped in Theravada Buddhism. To formally start the commemoration of the teachings of Buddha, the monks and Buddhist ascetics retreat from peripatetic lifestyle in a tradition called the beginning of Vassa or the start of the Buddhist rains retreat. From a Christian perspective, this retreat is equivalent to Lent.
This year, the beginning of Vassa 2013 falls on Tuesday, July 23, the day after Asalha Puja.
The Observance of Lent, the Buddhist Way

The period with which monks and ascetics retreat into sacred shelters is often referred to as the Buddhist Lent (although the label is anachronistic since Buddhism predated Christianity by thousands of years).
The start of the retreat is commemorated by Buddhist orders with the chanting of scripts and doing meditations afterwards. The rest of the rainy season is spent studying the scriptures in depth and engaging in intensive meditation. (The art of Thai massage, which started in temples, came out of the necessity to relieve sore and stiff muscles after hours of motionless meditation.)
Because monks do not go out during the period of the rains retreat, they cannot ask for alms from villagers they happen to pass by. Instead, it is the lay people who come to the temples to offer the monks food, robes, candles, incense and other basic necessities. Making merits during the beginning of Vassa is all the more important.
Buddhist Lent Celebrated by the Lay
Although the rains retreat is more of an event for those in the Buddhist order than it is for the lay, it is an occasion that reminds the devout to live the four precepts or truths of Buddhism. During this period, lay people may observe abstinence from alcohol and meat, and observance of chastity in thought and action. The lay may also opt to make merits as often as they can, since the rains retreat ends after about three months.
Asalha Puja
Lay participation during the Buddhist retreat is more obvious during the commemoration of Buddha’s First Sermon, or Asalha Puja, which is a public holiday in Thailand.
Because of this day off, workers go back home to their families in the provinces so they could make merits together. Families also participate in an evening candle-lighting ceremony called “wien thien” wherein people go to Buddhist shrines and circle around them three times carrying lighted candles. Lotus flowers are also offered and incense is burned on sacred sites. The lay may choose to listen to Buddhist monks chanting the First Discourse.
No Roaming Around During the Rainy Season
Theravada Buddhism arose in areas where the monsoons prevail for a good part of the year, making travel on foot more challenging. During the start of the rainy season, crops are planted in paddies, and this makes them vulnerable to monks who had to travel from village to village in order to teach the precepts of Buddhism.
The monks’ peripatetic lifestyle caused some farmers to complain to Buddha that their itinerant ways damaged crops and affected productivity. It was also getting difficult for monks to seek shelter under the shade of trees given this condition. Hence, Buddha declared that monks congregate in temples or shrines during the start of the monsoon and dedicate the rest of the season to prayer and meditation instead.