Fly Scoot during July school holidays, Perth to Singapore - $238 RETURN or $119 each way. This is the no frills version with no check in baggage, no food & no seat selection.
Example dates:
Depart Sat 5 July, return Thurs 10 July.
Limited seats available & I'm not sure when it finishes.
I don't recall seeing this advertised anywhere, maybe someone else has seen it…