Inside the bustling air-conditioned food court at the road-facing corner of Sultan Plaza is a Vietnamese food stall. At one glance, it seems to blend with the rest of the stalls but believe me, I know for a fact how authentic it is. This is because I use to frequent the Vietnamese eatery owned and run by this same hawker and his Vietnamese wife. It took up the ground floor unit of a coffeeshop in Joo Chiat. In fact, it was at the opposite end of the same shophouse row as the popular Long Phung. The hawker explained that the landlord took back the place so they had to cease operations. Anyway, the food he serves now is a distilled version of the large menu at the old location, and it's still as tasty as ever. Tweaked to complement the food court location and pricing, he offers simple and affordable one-dish meals (such as pork chop and lemongrass chicken sets at $5 each) plus a few dishes that are perfect for sharing (for eg. Vietnamese rice paper spring rolls at $5 for 4 pieces).
This is definitely a good place for lunch if you are in the area.