Need to consider the regulations of transit airports as well as the destination.

Turkish Airlines have good prices now (MAN-MNL) via Istanbul, there are currently no problems with transit in Istanbul for vaccinated passengers.

KLM have excellent prices (MAN-MNL) via Amsterdam with a "stop" in Bangkok.
- Thai entry controls would be in force for the short walk off and on the plane in Bangkok, which would seemingly require a PCR test before boarding the return flight in Manila.

Singapore might be difficult.