1

How long do you have?

2

And what sort of volunteering?

3

Flying can be expensive but you have to compare the prices.

Your first leg is from Singapore to Hanoi? This by train or bus is really pain. I would use a LCC for this leg.
From Hanoi to Hoi An you can use the train, no need to prebook. If you wanna catch a nighttrain that can be arranged 1 or 2 days ahead.
From Hoi An you can use nighttrain, but the scenic route is good for a daytrip too.
In HCMC you can use a bus to Pnom Penh and from there with bus or boat to Siem Reap.
From Siem Reap to Luang Prabang is again a little painfull since the road in Laos are somehow special. I heard about a boat connection from Vientaine, but that info might be outdated. If you wanna make that leg by bus, have fun, hell of a ride. As plan B you can catch a flight from Bangkok and back. Check with Laoair or Bangkokair.
To Pukhet is very easy. You can use bus or LCC.

I made this trip in 2 legs, each 4 weeks, so I suggest if you want to add some volunteering, you need at least 3 month.

4

Don't be scammed by the touting "Vietnam Adventure Tours"-caveat emptor. Avoid at all costs.

5

You will need to go to Da Nang to get the train to HCM City it takes anout 16 hours. Usually more. Bring a good book!

6

Thanks for you're advice! We're now booked from the 14th of january 2013 and our journey is for a month till
we have to return back to singapore -Aus. So volunteering might be a little tight fit, we were looking at finding orphanages and spending little but hopefully memorable time with kids or community building like some tours do.

What does LCC mean? So we are now booked from Singapore straight to Ho Chi Minh as we've seen singapore before. We now think going the reverse order will be better so plan is

Singapore-HCMC for a few days then to Hoi An for a few days then Halong Bay / Hanoi (however long it takes to see the sights we've got a few days in each or more) then from Hanoi I really want to try make it to Luang Prabang but flights seem so expensive so we are looking at flying from Hanoi to Cambodia mainly to see Angkor Wat
Then from there make our way to Phuket. Any suggestions?
How much does night train cost in Vietnam?

Thanks again!

7

Low cost carrier.

You possibly should read this and other easily accessible articles before you volunteer.

8

A bit of advice with orphanges. Don't give cash. It may disappear into the recipient's pocket. Provide food and clothes direct to the children if you want to help.