Xiengkhouang
Google
I spent twelve nights at the Sayo Naga, and it was more than satisfactory.  Everything (plumbing, air conditioning, even wifi) worked well, and though not fancy, it was comfortable and -- by Lao standards -- quiet.  There were occasional barking dogs, and one day I could hear rhythmic tapping from the Thitpheng Maniphone silver shop across the street, where artisans were doing high-grade repoussé work.  Any accommodation in town is likely to have similar sounds.  Staff were friendly and efficient, breakfast was consistently good, and laundry service was speedy.  I'd be happy to stay there again.