From Paris to Guangzhou arriving at 6 am, leaving to Indonesia the same day at 10pm.

Yes, you are eligible for the 72 hours free transit.
You can get the free visa when you arriving at the airport. You don't need other specific papers.
If you want to go to HK, you don't need to tourist visa.

Hello ZOE, thanks for you answer. I am sorry but I have read that the 72h free transit visa was only giving access to a specific region.
And that going to HK would necessite a VISA in order to re-enter on the CHina territory.
Can you please kindly tell me where you got this information from?
Thanks
Maxime

If you go to HK, the HK can be regarded your third destination, your itinerary becomes Paris-Guangzhou-HK, HK-Guangzhou-Indonesia, these are 2 transits and you need to apply for the stay permit again when you back from HK. However, the 72-hour free-visa transit is only available in Baiyun Airport, which means you can only visit HK by plane.

If you stay in Guangzhou and HK less than 24 hours, you are eligible for the 24-hour free transit and don't have to take a plane to HK.

As the French passport holders can visit HK without a visa at most 90 days, you don't need a visa to stay in HK. Anyway, if you still worried, you can apply for a visa in advance.