LOT Polish Airlines year-round Business class saver fares from Stockholm & Gothenburg.
The total price is slightly cheaper from Gothenburg but travel from Gothenburg involves long layover in Warsaw in both directions.
No buy latest date.

(Business) Stockholm/Gothenburg-Singapore R/T, LOT Polish, 1.585 EUR / 1.840 USD / 16.500 SEK incl. taxes

Airlines: LOT Polish Airlines (LO)
Cabin class: Business
Booking class: F
Fare basis: FASEY68
Fare: 11.800 SEK excl. taxes. Total from approx. 1.585 EUR / 1.840 USD / 16.500 SEK incl. taxes.
Advance purchase: 14 days
Min/Max stay: 6 days or stay the night between Saturday and Sunday / 12 months
Buy latest: --
Valid for departure: --
Valid for homebound: --
Stopover: One free stopover is permitted in each direction
Child discount: 25% discount from the base fare
Refundable: Yes, against a fee of 250 EUR
Rebookable: Yes, against a fee of 200 EUR each time
Routing: Stockholm-(LO)-Warsaw-(LO)-Singapore

Fare example: