Tranist visa requirement for Indian normal Passport holder at Kunming while travel by China Eastern

I intend to travel to Seoul from Kolkata (Kolkata-Kunming-Seoul) with a change over of flight at Kunming, both flights with China Eastern Airlines, with normal Indian Passport under tourist L.
Similarly, my return journey is Seoul-Kunming-Kolkata.
As per air tickets changeover period of 4:30 hrs (forward journey) while in return journey changeover period of 3:15 hrs only.

May please suggest whether transit visa (Double entry) for Kunming is required?
If yes, I apply for the same. If not required, then, is there any written document from Chinese Embassy or China Eastern Airlines.