Foreign cabin crew can be justified on routes with a specific language requirement, Japan for example. Jetstar however appear to be emulating the American cruise ship model where crewing is concerned. US officers, Bangladeshis below decks unseen and a mixture of nationalities in customer service roles carefully chosen so that they don't trust each other and won't unite and unionize. Chinese, Philippine, Vietnamese and Indians all speak different languages and each country has a territorial dispute with one or more of the others.
Classic divide and rule.