Join Date: Aug 2011
Location: Sydney, Australia and Stockholm, Sweden
Programs: VA Platinum, SQ Gold, TK Gold, Hhonors Gold, Accor Plus Platinum, Bonvoy Gold, Radisson Premium
Posts: 1,022
I don't see why not. When you arrive in SIngapore from Frankfurt, assuming you have time, exit immigration and go to the excellent first class check in area. Explain you are flying toe Jakarta and ask if you can check in now. If you don't have time for this you can check in online. All this assumes that you don't have luggage. But if you do you could still check in online and do a "bag drop" at Jakarta on your way back.
Good luck and let us know how it pans out.