We had quite a bit of trouble finding Na Dao restaurant (more about this and directions below), but it was well worth the trouble.
The affable owner, who is Lao and grew up in France, came to talk to us and take our orders. Although both Lao and French food are on the menu, we happily took the occasion to order the latter. Ostrich pâté, salade composée, duck, lamb, crême brulée, passion fruit mousse. Classical dishes, well-executed, good flavour and presentation, no surprises except, well, who would expect this in a provincial town in the south of Laos? And while the food and the ambiance were French, the attentive staff and the prices were definitely Laotian.
We took a tuk-tuk (I like the sound of that) to get there, since it is located a bit outside the central part of town where we were staying. It is, as some have said, close to the Champasak Grand Hotel and the bridge across the Mekong river. Our tuk-tuk driver had no idea where it was. The people he asked on the way didn't, either. At one point, he asked someone who vaguely pointed away from where we were. It turned out later that we had been right in front of the restaurant, but had not seen the sign, which is somewhat understated. When asking the driver to drop us off at the Champasak Grand in order to ask there, he proceeded to the Champasak Palace Hotel. Finally, at the Champasak Grand, a receptionist asked a colleague and was then able to come up with instructions.
So... Na Dao is indeed located across from the Champasak Grand Hotel, on a big intersection (one of the roads leads to the bridge across the Mekong from here). It is a bit far to walk from some of the hotels on road no.13, so if taking a tuk-tuk, ask someone to write instructions down in Lao. If you have your own transport, look for the intersection at the Champasak Grand. If you're staying at the Grand... just cross the road and walk to the intersection.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.