I will be travelling to Chengdu from Canada, via Shenyang. Then I will have a round trip to Thailand

Hi. I hold a Canadian passport, and I will be travelling to Chengdu from Canada via Shenyang(will not stay in Shenyang). Within 72 hrs of arriving in Chengdu, I will be going to Thailand for a 4-day vacation then come back to Chengdu. I only have a one-entry one, can I use the 72 visa free entry for the first time, then use my approved one for the 2nd time - entering from Phuket, Thailand? Also, the flight from Chengdu to Phuket is brought separately from the flight from Vancouver - Chengdu. will it still be counted as a transfer entry?