I have been reading numerous posts on this site in order to collate this itinerary that my girlfriend and I hope to follow (roughly) starting in March. We have left 10 days at the end in case we stay longer at certain places and also my girlfriend is keen to go to Hong Kong and go to Disneyland, I would not say no to going to a horse race meet at Hong Kong.
We have tried not to rush things too much and allow enough time for travel, especially within Laos, and also we have tried to split time off the beaten track with time on a beach/relaxing. We don't want to get "Templed Out" either so have tried to split this a bit as well.
We aren't too sure whether to go to Vang Vieng or not due to the mixed reviews, we may see how we are going at the time.
The italics are places where we can and possibly may skip depending on if we lose time in travel or stuff up along the way.
Fly from Melbourne to Hong Kong and get connecting flight to Hanoi.
Hanoi - 4 days 
Sapa - 3days (2 overnight trains)
Ha Long Bay - 3 days
Dong Hoi - 2 days (including travel)
Hoi An - 3 days (including travel)
Quang Ngai - 2days (including travel)
Nha Trang - 8 days (to Saigon utilising EasyRiders)
Saigon - 3 days
Phnom Pen - 4 days (including 1 day travel fromSaigon)
Sihanoukville - 4 days
Battambang - 3days
Siam Reap - 4 days
Laos Border travel 2 days
Si Phan Don (4000 Islands) - 3 days
Paske - 3 days(includingtravel)
Savannakhet - 3 days(includingtravel)
Phonsavan - 3 days(includingtravel)
Laupgrabang - 4 days(includingtravel)
Northern Thai Border 2 days
Tha Tong - 2 days(includingtravel)
Chiang Dao - 3 days(includingtravel)
Chaing Mai - 4 days(includingtravel)
Sukhothai - 3 days(includingtravel)
Bangkok - 4 days(includingtravel)
Thank you in advance for your help