When I am not flying Oneworld carriers, I have to use my Priority Pass to gain entry to third-party lounge operators to get away from the crowd.
When flying out of Changi Terminal 1, Qantas Business Class lounge is undisputedly the best lounge in the Terminal, if not Changi (don’t you remind me of Singapore Airlines’ Private Room).
However, when it comes to independently operated lounges, I have nothing but praises for the DNATA lounge. You get decent buffet offerings, an alcohol bar, comfortable sofas to relax, a dining area for your meals and also plenty of working space. The interior lightings are soothing and comfortable. You should be able to find rests even in the morning.
The DNATA lounge is located in Terminal 1. After Immigration, turn right towards D Gates, proceed to Mezzanine Level.