This is the Mekong Delta and anything you can get on dry land, you can find out on the water too. Having a boat in the region is a huge advantage for any industrious local who can afford to buy items he can then sell to those less fortunate (or tourists!) out on the water.
What to buy: Fruits and vegetables seem to predominate the market scene but you can find just about anything. Drink and snack vendors are not just serving tourists either. Locals need a drink too.
What to buy:
Go to the Snake Market and buy bottled snakes
You find them in any size.
Is colourful and will look good in your living room
After a few years you can drink the liquid (said to be good for the male potency) or pour it down the toilet because it stinks too much...
It's up to you
What to pay: very little, depending on the size of the bottle