Try routing through VIE with OS. They fly VIE-CMB nonstop twice per week. You can use that as your stopover en-route to turnaround in SIN, if I'm reading the original post correctly.
BSL-x/VIE-CMB-SIN-x/FRA or VIE-BSL - or vice-versa if you want to do SIN before CMB. On the return OS fly CMB-MLE before heading back to VIE though. First option should be direct routing and also well within mileage.