Sandals. You'll cover a lot of ground in Vietnam, so think about a versatile, open-toed sandal. It’ll keep you cool, comfy and offer you a bit more support than a pair of thongs. Find a pair that will work well during the day and won't be out of place at night.
Closed-in shoes. They'll be times when you'll need a bit more protection. A good runner or trail shoe won't be amiss, but consider a smarter travel shoe that can do multiple things at once.
Hiking Shoes (optional). If you have a specific hike or trail or mind, research the kind of weather and terrain you can expect. In some instances, a lightweight trail shoe will be enough, but if you've got something big in mind, you'll need a proper hiking boot.
Merino socks. If you're wearing closed-in shoes at any times, treat your feet to some merino socks. They'll wick sweat away from your foot, minimise the dampness and help keep blisters at bay.