The Thao takes ancestor worship as the main theme of their religion. The highest ancestor spirit Pacalar is thought to live at red cedar tree on Lalu Island. The second level spirit is ancestor of each clan. In Barabaw there are four ancestors of five names’ clans, they are Yuan’s Mashqashqa, Mau and Shi’s Amulish, Chen’s Fuliti, and Kau’s Malhipulu. The lowest spirit is Apu who abide in ancestor’s basket (ulaluwan) in every house. Each Thao becomes apu after he/she dies. In fact, the Thaos call their grandparent and elderly “apu” too. They think that each level of ancestor spirit has its own equivalent power to exorcise evil spirit called “gali” and to endow luck to Thao family and individual. In ordinary life, all kinds of life rites, farming rituals, the eel rite for hunting, and worship of ancestor need Shinshi to hold ceremony by facing ulaluwan of each family.

There are several premises to be a Shinshi (female priest):
1. The woman must be married and has children.
2. Her husband is alive and healthy.
3. The couple had been sponsors of an annual ceremony of ancestor worship.
After showing her willingness, she should pass several special rites. The major one is that led by senior Shinshi, the candidate goes to Lalu where she should be recognized by the highest spirit i.e., Pacalar. Then she may be trained to be Shinshi by a senior priest.