Bangkok - Guilin - Taipei with 72-Hour Visa-Free Transit stop in Guilin

I'd like to find out if it is a feasible plan to fly from Bangkok to Guilin, although the flight isn't direct and has a layover in Nanning before arriving in Guilin. Will I have to pass passport control in Nanning or Guilin? I would like to spend 72h in Guilin. And then fly out to Taipei, Taiwan.