The annual festival is the biggest held by Thai Den people in Muong Lo.

On the 10th and 13th days of the 7th lunar month, each local family prepares banana leaves, sticky rice, chicken, peanuts, and many more ingredients to make Sip Xi sticky rice cakes, the most important feature of the festival. The cake is not only used for ancestral worship but also presented as gifts to relatives, family members, and esteemed guests. Thai women also gather various types of leaves to make colorful glutinous rice dishes as offerings to their ancestors.

According to the Thai people's belief, the month of Sip Xi is meant to summarise the harvest season and pray for happiness, abundant rice crops, and healthy cattle. During each festival, Thai families also cook a few ducks to drive away bad luck and misfortune in life.

In addition, they prepare alcohol, meat, fish, and other dishes to treat their friends and guests. Arranging offerings for the ancestors, people clean and decorate their homes, alleys and fields.

On the first day of the festival, the head of a household invites the ancestors and spirits to come back and join the celebration with their descendants. The next ritual is called "Tam te", with a plate of glutinous rice and chicken placed on the edge of the family's paddy field. The shaman sits in front of the field, paying respects to the village spirits and ancestors, and praying for the protection of rice plants.

At night, everyone joins in the festive atmosphere, performing various Then dance moves and engaging in sports, cultural activities, and traditional games.

Traditional folk games reenacted during Sip Xi festival.