HNL to NGO to PEK and then 2 days later fly from PEK to REP

I will be flying from HNL to NGO to PEK. I would like to use 72-hour Visa-free Transit to visit Beijing area for 2 days. I will then fly from PEK to REP. I plan on attaining the Cambodia Visa upon arrival at the REP airport. Am I eligible to receive the 72-hour free transit for Beijing? Or do I need to attain the Cambodia entry permit in advance?

Thank you, Pat