Cambodian Passport holders needs to apply for a transit visa?

I would like to check if Cambodian Passport need to apply a transit G if they flight out from Phnom Penh to Narita (Japan) through Shanghai (China). Here's the flight schedule
1. MU 760 PNHPVG HK3 0015 0455
2. MU 523 PVGNRT HK3 0910 1250
3. MU 272 NRTPVG HK3 1055 1320
4. MU 759 PVGPNH HK3 2000 2315

PNH= PHNOM PENH PVG=SHANGHAI NRT=NARITA