Question-Does it have to be booked as stop-over?

Hi!

I'm planning to book a flight from AMS to BKK and then after two weeks from BKK to PVG, with a few days in Shanghai and then from PVG to AMS. I can book the return flight from AMS-BKK and PVG-AMS but I was wondering if I may book a separate one-way flight from BKK-PVG and still use the 144 hours visa as long as I have a confirmed onwards flight back to Amsterdam?