You have the OW options except the JAL lounge:
British Airways Lounge
Location details: Airside
Opening hours: Daily: 15:00-23:59
Notes: Construction of a new Singapore Lounge is currently underway. Eligible passengers may be directed to an alternative lounge.
Business CentreFree WifiFood and BeveragesShowersWheelchair AccessTV
Malaysia Airlines Golden Lounge
Location details: Level 3, Transit Hall, Terminal 2, Changi International Airport
Opening hours: 5.00am to 9.00pm Daily
Business CentreFree WifiFood and BeveragesShowersKids ZoneTVRelaxation Room
SATS Premier Lounge
Location details: Terminal 1, airside, west side, Level 3
Opening hours: Daily: 24 hrs
Operated by a third party on behalf of: Japan Airlines
The Qantas Singapore Lounge
Location details: Terminal 1, turn left after immigration, up escalators
Opening hours: Daily: 14:30-23:00
Free WifiFood and BeveragesPreflight Dinner OptionShowersWheelchair AccessTV
The Skyview Lounge
Location details: Terminal 1, airside, mezzanine level, close to gate D30
Opening hours: Daily: 24 hrs
Business CentreFree WifiFood and BeveragesShowersWheelchair AccessTV
And the EK lounge upstairs from C1 which will probably closed for you:
