Thai corn and Viet corn are so popular in winter in Hanoi. The sellers will try to tell you that they are selling Thai corn instead of Viet corn saying it is sweeter and therefore more expensive. To make sure, you should try one seed. Thai corn is usually bigger than Viet corn. Even the corn water in which the corn is cooked is sold. It is really sweet, healthy and lots of people drink it with ice or warm.
When eating, you can choose between steamed corn and grilled corn. The steamed corn is more popular on the big streets in the city than grilled corn. They are normally the same price - just cheap.