Your best bet is probably to just pick something that fits your budget constraints from a travel reservation website such as e-long or c-trip and take a taxi to the hotel when you arrive. They will have taxis at the airport even though it's late at night.
Alternatively, if you are traveling light and speak Chinese, just wing it and find something after arrival.
The international flight terminal and the domestic flight terminal in Kunming's airport are in the same building and very close to each other. It would not be difficult to retrieve your luggage and re-check it, but that really should not be necessary. If you don't plan to spend time in Kunming, why not just check it through to your final destination (Chongqing) when you board your Vientiane flight? That would be the simplest thing to do.