Bangkok-Hong Kong-Beijing-Hong Kong-Bankok. Can I use the 72 hour visa-free transit?

Hello. I am 17 years old. I want to visit Beijing for 2 days to see my father (who works there). I will fly from Bangkok with 2 hour stopover in Hong Kong (I stay in HK airport only) before continuing flight to Beijing. I will stay with my father in Beijing for about 40 hours and then return to Bangkok (with 2 hour stopover in Hong Kong--I stay in HK airport only).