Luang Po Phra Sai, a large Lan Xang–era Buddha image awash with gold, bronze and precious stones, sits at the hub of Nong Khai's holiest temple. The head of the image is pure gold, the body is bronze and the ùt·sà·nít (flame-shaped head ornament) is set with rubies. Due to the great number of miracles attributed to it, this royal temple is a mandatory stop for most visiting Thais.

Luang Po Phra Sai was one of three similar statues made for each of the daughters of Lao King Setthathirat, and they were taken as bounty after King Rama I sacked Vientiane in 1778. The awesome murals in the hall housing the Buddha image depict their travels from the interior of Laos to the banks of the Mekong, where they were put on rafts. A storm sent one of the statues to the bottom of the river, where it remains today. It was never recovered because, according to one monk at the temple, the naga (which live in the river) wanted to keep it. The third statue, Phra Soem, is at Wat Pathum Wanaram, next to Siam Paragon in Bangkok. Phra Sai was supposed to accompany it, but, as the murals show, the cart carrying it broke down here and so this was taken as a sign that it wished to remain in Nong Khai.