Nope, they can get TR60 multi entry which used smartly gives then nearly 9 months in Thailand. Stay 90 days leave for 24 hours come back do another 90 days leave and come back couple of days before visa expires will give them another 90 days, no need to do 3 months anywhere else
it's needed if your able to get insurance in Australia but I could not find any that would sign the required paperwork. Hence best to just do thai insurance.