Southeast Asia forum

Looks like a pretty organised trip . still a lot of travelling for 2 months.
I took the overnight bus once from Hanoi to Vientiane (approx 22h) so I think there should be one the other way around as well.
I'd pick a day of from Chiang Mai and add it to Hanoi (as you probably want to go to halong bay as well)

It all depends on what you are looking for of course, but if it were me I would tend to ...

- cut Hue back to 2 nights, and add an extra night in Hoi An
- consider one less night in Nha Trang. It really isn't that special....
- double-check your plan to get from HCMC to Kep. Not sure how you can do this.... (not saying you can't, just not sure how it will be done unless you go via PP)
- only two nights in PP might not be enough, depending on your plans. One day spent getting there, one day getting from PP to Siem Reap leaves one full day in PP, which presumably will go to S-21 and Killing Fields. Doesn't leave much time for anything else. That may be OK, but just be aware.

In fact, you need to consider that a day is spent travelling between most places, but the time you get to the bus station/airport, wait, travel, wait, get checked in to the next place, etc. 4-hour travel time is NEVER 4 hours! When planning, I like to count up the number of FULL days spent in each place, then consider the sort of activities that you want to do there and be sure you will have enough time to accomplish everything WITHOUT running yourself ragged trying to do it all. I'm a big believer in building in a couple of days R&R time every week or two otherwise you can burn out.

(BTW - I've only reviewed the that places that I have been to as the basis of my comments - ie Vietnam and some parts of Thailand.)

Look at it this way: you can always come back to Vietnam for another trip. That means you that you can have a trip dedicated to Vietnam and more importantly it gives you something to look forward to when you come back from the first trip!