144 hours after an X2 visa

Hello !
I am in Beijing with an X2 for 6 weeks, as an exchange student. I want to visit South Korea.
Since my X2 has a single entry, I want to use the 144-Hour Visa-Free Transit to come back from Seoul to Beijing just a few days before I can leave with my direct return flight to Paris. Is it really possible in this specific situation ?
If so, what papers can I bring, besides my return flight ticket to Paris ? I don't have a Temporary Residence Permit. Should I get one ? I only have the paper of the International School Dormitory specifying I am staying there for 2 months.
Thank you for your help...