Hmmm for hotels then not sure. But if you are just in lounges there are several pay in lounges... what terminal are you - T1? You can transit between T1/2/3 airside anyway by the train.

I have priority pass so there is at least one lounge in each terminal run by SATS or CIAS. Quite a few of them take some sort of credit card, or you can pay in for around $20 from memory. Changi Airport website should have more details. There are also transit hotels, massage areas or fish pedicures where little mini fish eat away at your feet haha

Keith Urban is great, but i'm more looking fwd to seeing Lady Antebellum as the warm up act. It was a V Day present from the gf