i reaching perth in midnight will i able to get a tourist sim card at the airport? pls advice
I doubt it. Think you will need to wait until the ne t day.
There are both Vodafone and Optus stores at T1 International which will be open. There is a Link conveneience/newsagency/technology store at T3 if you arrive there which may have pre-paid sims.
You can discuss your requirements with the staff at any of the stores and they will suggest an appropriate sim.
Alternatively, wait until the next day and visit a shopping centre near your accommodation and call in to any one of a myriad of phone retailers.
Damn, Optus closes at 2am everyday. That's a tough gig.