This is the boat we took from Luang Prabang to Nong Khiaw along the Nam Ou River. It snugly fit about 12 people their backpacks. We were all sitting on remarkably tiny kindergarten style chairs - amusing for the first couple of hours, then the leg cramps set in...
That said, the trip was terrific and worth every bit of discomfort. The scenery, including the landscape and people-scape, was impressive.
Oh yeah, no bathrooms on board (obviously due to a severe shortage of space). When the boat finally made a pit stop (4 hours after launch), the urgency and pending relief was palpable. We haven't seen people move like that since the Black Friday release of the Cabbage Patch Kids.
Read more about this boat ride from Luang Prabang to Nong Khiaw.