I recently bought a Minsk in Hanoi and rode through all these countries
Here are some things that may help
Viet-Nam is the main problem as border crossings with a bike is sometimes difficult and as I wanted to ride back into Viet-nam, ( make sure you get multi entry visa), buying in country was the best option. If you do decide to buy, Hanoi is an advantage as district plates (29 ) will help with authorities throughout the north and south.
There are many places to rent rooms though they are not advertised well, learn the different names for the different districts.
Border crossings- North is open (Den bien to Udamaxai, Laos) beware the road deteriorates on the Laos side for 100ks then ok.(Bribe warning)
South - Bo-y is under a lot of construction so only roadside shacks for Laos and a simple process on the Viet-nam side ( this is a great ride )
Centre- Khe-san to Laos very efficient no waiting
I took the bike through the
Laos-Thailand borders at Vientienne to Udon Thani here make sure of your papers (owernship mainly) I was rejected at the
Cambodian-Thailand border (Siam reap to Thailand) but there are border tensions there ( Siam Reap means "the defeat of Thailand" after all)
Thailand to Laos at Savanakhet across the friendship bridge -sweet- carry spare photos if no visa
Viet-Nam to Cambodia no problems (A vaccination-health card helps here)
Cambodia-Laos primitive (bribe warning)
Cambodia and Laos are a doddle to ride around (mainly flat), if you keep to the main drag , if you travel off season, make this gospel.
Thailand is a shock if you have been riding in Laos-Cambodia, very modern, very fast and this is where a small bike is found lacking. There are dedicated bike lanes though.
What I would do different next time-
Bugger the Minsk Its cheap but its old tech and will give you problems. I will get a hero honda or something, more expensive but reliable ,parts everywhere, NOT a smokey, noisy two-stroke A small bike ,imo, goes as fast as you should when travelling in SE Asia. Also it is easier to lift them onto canoes, ferries,trucks etc.
I would avoid the main highway in Vietnam, its a bitch (although there are some special vistas sometimes) I prefer the mountains , the Ho Chi Minh trails (there are many) Not easy, but an adventure.
If Asian city traffic worries you, just get up real early and make the city limits just on dawn.
If you have any specific questions I would be happy to reply If I'm able.
BTW I'm jealous , your're about to have the time of your life
