Daeng Naem Neuang is probably Nong Khai's most famous restaurant, and it specialises in the Vietnamese dish naem neuang — grilled pork rolls that you wrap yourself in rice paper with fresh herbs, cucumber and a sweet-sour dipping sauce. It is simple, interactive, and very good. The restaurant has been around for decades and is well known among Thai travellers passing through on their way to Laos.
The portions are generous and the prices are low. You will likely share a table with Thai families who have made a detour specifically for this. Find it in the town centre, not on the riverfront.