You need offer your departure date since the flight varies day by day. For example, in July, direct flights from Singapore City to Kunming are available every Monday, Thursday, Friday, Saturday and Sunday.
Every Monday, Friday and Saturday, China Eastern Airlines provides flights between the two cities and the schedule is: departing at 02:20 and arrival time is 05:40 (Mondays and Fridays), departing at 03:15 and reach Kunming at 06:40 (Saturdays).
On Thursdays and Sundays, MT airlines has flight respectively at 08:10 and arrival time is 12:10.

If you do not need direct flight, you can transfer at Chengdu, Beijing, Bangkok and Kuala Lumpur.