Originally Posted by
rozy
Although SQ is *A, my personal experience tells me that they don't connect luggage to other airlines in normal circumstances.
Just to make it clear that SQ staff will not be not be involved nor make any decision about whether or not to check bags to final dest. It will be the check-in staff at TXL, which is neither SQ nor TK staff, but contracted staff at the check-in counters that decides if your request will be accommodated. You should be able to show the onward ticket, IST-SIN with SQ at the TXL check-in counters.
If you ask nicely there is a fair chance that they will tag bags to final destination to save you from entering Turkey to pick-up your luggage for re-check-in with SQ at IST.