yes but unfortunately the lounge closes from about 1am-5am. there is an airside transit hotel, but I've heard it's expensive.
Good point, I think the airside hotel is this: Louis' Tavern Dayroom & CIP Lounges : Thailand's Transit Hotel at Suvarnabhumi Airport It does look to be 24hrs, but as you say not cheap (eg. AUD150+ for 8 hours)