Wat Lam Kuan
There are a number of small temples around Nong Khai city. The one you're most likely to notice is Wat Lam Kuan, due to the giant golden Buddha statue perched on the roof of one of the chapels. You can see the Buddha from a distance, and it's only a short walk from the end of the riverside market area. The big Buddha sits on top of a rather ornate chapel, which usually seems to be closed.
Next to this temple is a Chinese shrine with a rather nice old tree next to it, festooned with red Chinese lanterns. Beyond that is yet another Thai-Chinese Buddhist temple.