Hi there,
I have also been performing numerous Bangkok/Singapore trips of late.
For lounge access at both these (and the Aussie airport) airports (when flying economy), I have taken up these offerings:
1. I purchased the US Airways Club membership. It allows Lounge Access to any Star Alliance Lounge if flying on a valid economy Star Alliance ticket. I saw the offer on this thread,
http://www.australianfrequentflyer....star-alliance-lounge-access-259usd-29285.html but it may not be the same price now. For frequent trips though, it has proven really good value. I have road-tested it at MEL (Krislounge), BKK (Thai Orchid) and SIN (Star Alliance Lounge). All lounges granted admission OK, but best to take documentation, just in case the lounge staff are not aware of this arrangement.
2. If Flying Qantas/JetStar, you obviously have the Qantas Club. If no Qantas Club Membership, then you can buy the JetStar Business Max tickets on the MEL-BKK JQ flights.
The only other carrier from Oz to BKK is the EK flight from SYD, but I've never really liked the arrival time of this flight into BKK; so I haven't looked at lounge options for EK.
Funny thing about the BKK TG Thai Orchid lounge.....they did not serve wine. Beer, spirits yes, but no wine. I'm unsure if this was a temporary policy, or if it has always been like that.