Some of the legacy airlines have what might be commonly referred to as "open jaw returns", namely fly out to one airport and fly back from another.
Most recently I used an open jaw return with Air France KLM, and because the fare was some £200 cheaper routing via CDG rather than direct from AMS to SIN I routed, on the outbound, CWL/AMS/CDG/SIN with AF and I returned MNL/AMS/CWL with KL and all on a cheap (ish) economy return.