I used to get coverage with 12call in Aus off the vodafone network, and be able to receive and send messages to friends in Thailand etc from it, now I recently have arrived back in Aus, but no signal for 3 days, both sims are inactive, and phone says emergency calls only, has anyone heard anything about 12call terminating their coverage in Australia at all??

no one?

According to be AIS International Roaming website they have roaming agreements with Vodafone Network PTY, Telstra Crporation and Singtel Optus

http://www.ais.co.th/interservice/en/otc-roamingabroad.shtml#!prettyPhoto/0/

You have to request international roaming be activated on your SIM, http://www.ais.co.th/interservice/en/otc-howtoapply.shtml

you need to have an unlocked phone and coverage, an active SIM which has balance and has not expired. You may have to manually select a network.

I suspect it is some issue related to your account, equipment or location.