One-entry visa and then go back to mainland China just for transit

In reality, your situation is very simple.

You will use your single entry visa for your first part (visit) to mainland China. You will travel to the cities where you want and after that you will travel from Shanghai by plane to Hong Kong. At the moment when you board the plane for Hong Kong, your visa will expire.

So, after your stay in Hong Kong, you will depart for Kunming and then to Myanmar. Also, you plan to stay for some time in Kunming.

This is all allowed and if you don't have any additional landing within mainland China during this route, you will be definitely eligible for 144 hour visa free transit in Kunming and you don't need any kind of visa. You have to know that 72 hour visa free transit in Kunming has been replaced by 144 hour visa free transit for some time.

So, you will print out your flight tickets for your route from Hong Kong to Myanmar and you will bring those printouts with you. Also, you will declare at check-in in Hong Kong that you will travel to Myanmar via Kunming using 144 hour visa free transit. After a short inspection, you will be allowed to board the plane.

Upon your arrival in Kunming, you will approach 144 hour visa free transit counter where you will fill out the blue form. Shortly after, you will get a sticker in your passport and you will be allowed to exit the airport. That's it.

To conclude, a single entry visa you have right now is more than sufficient for your planned trip to and through China.

Thank you Zupan. Very helpful. Could I ask you as a last question: is it mandatory for me on my single entry visa to leave China (ie Shanghai -or wherever else in mainland China- to Hong Kong) by air? Do you know if I can travel to HK by land? Now my visa has already been granted so I am wondering whether leaving by air to HK is still mandatory. Thank you :)

If you enter with tourist (L) visa then you can leave to HK by foot if you wanted to.