2.5 weeks : not sure why you think you can d Vietnam in a week. I honestly can't imagine how anyone could travel a country this size in anything less than 3-4 weeks at the very minimum.
If I were you I would do this:
Bangkok- 2 Days (get your onward tickets here, much cheaper)
Cambodia - 3-5 days
Laos - 3-5 days
Vietnam - 7-10 days (go to Hanoi and Danang/DmZ/Hue if possible all in North)
You live in SE Asia now, its time to see it if you can. If you enjoy beaches, you can spend 2.5 weeks in Thailand very easily.
If you are a diver, then Micronesia is great.
If you enjoy culture, then 2.5 weeks in India would be great.
Anyway, lots of places to see and 2.5 weeks is not much time to do it in.
[This message has been edited by swordfish (edited 13-05-2005).]