Most cyclists in Laos stick to the main Route 13, which runs the length of the country from south to north.
It’s paved, in good shape and traffic is light. The few cars and trucks on the road go relatively slow and give cyclists plenty of space when passing.
Go off the main road and it’s a different story. Your back road will almost certainly be dirt and little more than one big mud puddle in wet season. It may not even exist. Triple check with locals before heading off onto a road that looks promising on your map. Just because it’s marked as a big red line doesn’t mean it’s at all suitable to cover on a bicycle or that construction has even been finished.
As an example of how misleading maps can be, we were planning to cover Route 23 in southern Laos until we met someone who had just come from that road. She had to walk for two days because there was nothing more than a forest path and this was an allegedly major road on our map. We later saw pictures of the road and it was just a rocky, sandy track.
Maps of Laos are almost impossible to find in the country. Bring one from home or just wing it.