It has been the custom in some wats to hold a festival of building "phrasai." Phrasai" is an abbreviated form of "phra chedi sai" (sand-pagodas). " Phrachedi" means pagoda and "sai" sand. This festival takes place on an open space in the wat. The sand to be used for the occasion is provided by the wat and piled up nearby. The pagoda builders, mostly women and children, will come to the wat in their best clothes. They will buy candles, joss sticks, flower and banners from the wat stalls set up in the compound. Buying these articles from the wat is regarded as "tham bun" ("merit making"). Some will bring along these requisites, but nevertheless, they will contribute money to "tham bun" as well.

Before the people start to arrive, some monks prepare the temple compound with piles of sand. While others make the flags that will be stuck in the "sand pagodas".

The merit makers will then fetch sand in the silver bowls which they have brought along with them and carry them to the ceremonial ground and start building a sand pagoda something like a pyramid. The size of the pagoda is optional. The sand is mixed with water to make it lump together when used to build the pagoda. A coin and and a leaf of the religious fig tree will be buried inside the sand pagoda. When finished the pagoda is sprinkled with scented water and decorated with flags and banners. The base of the pagoda is then covered with a small piece of yellow or red cloth. Lighted candles and joss sticks and flowers are stuck around the sand pagoda as an offering. Some of these pagodas, usually the big ones, are beautifully decorated with miniature ceremonial latticed fences surrounding them.

Once the "sand pagodas" are finished, lighted joss sticks are placed in the sand as well as flags with money attached to the stem. As the joss sticks are placed into the sand, the builders say a small prayer.

Sometimes people vie with each other in building such pagodas. The ceremonial ground itself is decorated with ceremonial latticed fences called "rachawat" and banners. There is a theatrical performances in the wat on that day for the merit makers to enjoy themselves. It is a one-day festival and the wat benefits by the sand which the devotees bring. For it serves to raise the level of the ground which normally is too low during the flood season. As the open ground in the wat also serves as a meeting place for the community during the religious and festive occasions, it is ultimately the public in general who benefit by this religious custom.

Building the "sand pagodas" is a family event that goes on all afternoon. As the sun goes down, everyone stops and a prize is given to the best "sand pagoda".

The sand pagodas do not last long. Unless they are jealously guarded, mischievous children will take pleasure in prying them open and thus ruining them in order to get the coins inside. The bigger ones are usually the selected targets.