Why Nong Khai has so many temples has never been adequately explained to me, but maybe the mysterious and magical river has influenced this surfeit of spiritual expression.

The roof of Wat Lam Duan has paid the greatest tribute to the river. For its Buddha image sits up there on the Bot (Chapel) and gazes over the Maekong to Laos beyond.

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Temples

Nong Khai is famous for having one of the highest number of temples per head of population in Thailand.

The most famous temple is Wat Pho Chai as it is the home of Luang Pho Phra Sai. Commissioned by the three daughters of the King of the Lao Lan Chang Empire, it is one of three identical Lao Buddha images, one of which fell into the Maekong during a storm 200 years ago. Its head is said to be made of solid gold! (pictured below)
The prize for the prettiest temple would probably go to Wat Tung Sawang. Its tiny but immaculately sculptured chapel with highly detailed porticos, and its collection of Buddhist deities outside, each under its own fanciful little roof, gives it an Alice in Wonderland bizarreness.

Even if you've seen a lot of temples it's worth visiting... (pictured below)

Sala Jao Phu Ya is the Chinese Mahayana temple and, unlike some Chinese temples, is kept doll's house perfect. Nong Khai has a strong Chinese and Vietnamese population who originally would have been Mahayana Buddhist. (see Chinese Dragon Festival)

However, most happily go to see the monks at the Thai Theravada Buddhist Temples, but a few still like to retain their old culture.

Wat Nern Panau is the leading meditation temple in Nong Khai. By providing accommodation in the form of small bungalows, it is a place where those who need to retreat may stay for a while. One is expected to stay confined and to meditate in order to break with ones past problems, so that a clear fresh start to life can be made.

The architecture is spectacular with long beautiful cloisters, a very vertical bot (chapel) and shrine with extensive use of gold stenciling.

Set in some natural forest, the whole atmosphere is somewhat mysterious, though its imposing buildings are rather sombre. Ask for instructions how to get there, as it can be a little difficult to find.
With over 30,000 temples in thailand, visiting them all is an inexhaustable endeavour. That being said, a few others we could recommend making a trip to are; Wat Phu Tok and Wat Hin Maak Peng, which is 2 hours west of Nongkhai.