The Luang Pho Phra Sai, cast from yellow gold in the posture of Subduing Mara, is centuries old dating back to the ancient Lan Chang Empire.
The legend goes that the three daughters of the King of Lan Chang commissioned three such images of the Buddha were given names corresponding to the names of the three daughters, Phra Some, Phra Suk and Phra Sai.
There is a large mural housed at Wat Pho Chai that was painted as a historic record of this event. The three images, originally housed in Vientiane, were brought to Nong Khai over 200 years ago, during the reign of King Rama III .
However Phra Suk fell in to the river during a violent storm whilst in transit to Nong Khai by boat on the Mekong. The two Surviving image were placed in Wat Pho Chai and Wat Ho Klong.
Later, during the Reign of King Rama IV, Phra Some was taken to Bangkok, leaving Phra Sai at Wat Pho Chai.