The AY flight gets into SIN at 18:15, and as you are going to OOL, I would instead get QF52 (BA codeshare BA7352) from SIN (21:20) to BNE (06:45) and catch the train from BNE down to the Gold Coast.

Train timetables can be found here:

http://www.airtrain.com.au/Uploads/C...0to%20City.pdf

Catching the 7:29am train will get you down there around 9:00 - 9:10am depending on where you want to go in the Gold Coast.

This would spare you the Jetstar ordeal! The train provided is pretty good and leaves just outside the terminal so its a good option.

There are no direct flights to BNE from BKK so that takes that option out unless you want to transfer via either MEL or SYD onto a corresponding JQ service.