Na tej trasie jeździ polecana w Internecie firma Asia Van Transfer (sporo dobrych opinii mi. TripA.)
Korzystają z wmiarę nowej, północnej trasy. Podróż z Siem Reap na granicę kambodżańsko-laotańską zajmuje 5.15 h i kosztuje 16$. Z tego co rozumiem dalej bus jedzie przez 4tys wysp do Pakxe.
Można rezerwować miejsca w busikach pisząc poprzez formularz na stronie.


Siem Reap --> Don Det/Don Khone (4000 islands - Laos) 08:00 am 04:15 pm

Don Det/Don Khone (4000 islands - Laos) --> Siem Reap 08:00 am 06:30 pm
Border Laos/Cambodia -->Siem Reap 11:45 am 07:00 pm

http://www.asiavantransfer.com/index.html

Southern Bus Terminal
The Southern Bus Terminal (Dong Dok) is the main departure point for all destinations in southern Laos and international services to Vietnam and Cambodia. It's located 11 km north of the downtown core, straight up Kaysone Phomvihane Avenue from Patuxai monument. Tuk tuks will ask for 50,000 kip to take you there. An alternative is to take the green and white city bus #29 from the Central Bus Station for 4,000 kip. Buying your bus ticket from a travel agency will cost more but again, it includes a transfer to the station.
Sample destinations include:

Pakse (local bus) departs 10:00,12:30,13:00, 13:30, 14:00, 14:30, 15:00, 15:30, 16:00, takes 12 hours, 110,000 kip
Pakse (Express) departs at 18:00, 19:00, 20:00, takes 10 hours, costs 140,000 kip
Pakse (VIP) departs at 20:30, 21:00, takes 12 hours, costs 170,000 kip

Services to Cambodia
Phnom Penh (sleeper) departs at 20:30, takes 24 hours, costs US$45
Siem Reap (sleeper) departs at 20:30, takes 25 hours, costs US$50