At left: If you're mad, lazy or a complete newbie, you can get the boat from from Kratie or Stung Treng to the Lao border.
In actual fact, it's a valid option, 'cos the road from Kratie/Stung Treng to the border is pretty tough going, and you might die out there. So...
In Steng Treng, you get the boat at 7 AM at the pier in front of the Sandon Hotel.
take 2 hours, cost 35 dollars for the boat, and will take about 5 people
(or maybe 4 people and one bike).
(shown at left) take 4 hours, cost 5 dollars per person and a dollar
for the bike and hold about 25 people.
Take some food and water with you for the trip.
At the border:
The boat will dock at the Cambodian Immigration hut on the west bank of the Mekong.
It costs nothing to exit Cambodia once your Exit Visa is in place, but the border guys may try to fleece an extra couple of dollars out of you. Mr Pumpy says: Be polite, but firm and say NO!
The boat will then take you across to the Lao side on the east bank of the Mekong.
There is a Guest House on this side of the river (actually still Cambodia) and you may be able to stay the night if need be.
The Lao Immigration hut is a kilometre up the dirt track and it will cost you 5 dollars to enter Lao. This is a standard charge. Welcome to Lao!
Note that this Mekong border crossing is different than the Highway 7/13 road crossing, a few kilometres to the east.
Highway 13 is wide, sealed and in great condition. The turn off for Don Det is 8 km and Koh Kong is 29 km from the Lao border post. Pakse is 154 km away.