The Thai International flight takes less than two hours to get to Kunming.  Kunming itself has little to offer but there is a great deal not far away.  I would advise hiring a car and driver and making the four hour loop which includes the Stone Forest and the caves and waterfalls.  In general, I find caves boring, but these were not.  Of course, you have to allow more than the four hours so you can walk around and not be rushed.  In other words, it is a day trip out of Kunming, back in the late afternoon.  And well worth it.  At one point, there were chair-bearers inside a cave and the idea was you pay them to take you up the area with a hell of a lot of steps.  I didn't take them but yes it was a hell of a lot of steps and the climb was safe but steep so I had to stop a few times and wait for my heart to slow down to normal.