As part of our RTW trip, on our SE asia leg we want to fly into Hanoi, travel down to HCM, take a boat trip to Phnom Penh (any recommendations please?) then up through Laos. Then is it possible to fly to Hanoi and immediately fly out back to KL or singapore?
We dont really want to pay another visa for entering Vietnam, would we have to if only flying in then flying out?
You won't need a visa if just stopping at the airport, but if you are stopping for a second visit that might be a different story. A standard 30-day visa might cover you for multiple entries but i didn't do it myself so my memory is a little fuzzy...can find out easily enough from a travel agent if it comes to that. I flew into Hanoi from Bangkok but they probably have flights to other asian cities, being an airport 'n' all. Vietnam is the greatest.
HCM to Phnom Penh i went down to Chau Doc for a boat then bus to PP... about 6 hours on a single ticket, then later up to kratie and stung treng for the laos crossing....