Hong Kong, Saigon (assuming you are on a small ship), and Singapore you dock right in the city. Bangkok is very far from the port. If you are overnighting, recommend hotel ashore. For Danang and Hue, you often dock in Chan Mai [sp] that is half way in between; not too bad of bus/car ride.
The flights can be long. If you can swing non-stop to Hong Kong; that makes things easier. We had problems with our flights to Hong Kong and didn't see our bags for 10 days; they arrived in Saigon. From Singapore, there are also non-stop flights back to US.
This is a wonderful trip. Assuming overnights in most ports, you will see a lot. An extra day or two on both ends would also be great. After this cruise, we added on Angkor Wat which was fantastic.