I am German and I am holding two valid German passports. My first passport (Passport A) contains a Chinese visa. My second passport (Passport B) is still empty so far.
Now I want to travel from Germany to Singapore and move on to China from there.
My plan is to fly to Singapore and enter with Passport B. When leaving, I need go to China with Passport A (as it contains the visa - I can clear immigration with passport B in Singapore).
Are there any problems about this plan, at the check-in in Singapore, immigration in Singapore or immigration in China? If I check-in with Passport A, I can't prove legal immigration to Singapore (as the stamp is in Passport B) If I check in with Passport B, I can't prove I hold a valid Chinese visa).
Will the problem be solved by presenting both passports? Which passport should I book the flights on?