Garuda terms and conditions, along with other Indonesian airlines are well below world standard. However you need to factor in the relatively low cost of living for a local. A narrowbody captain may be on considerably less than a European Airline would pay but would be able to live in a mansion with a couple of servants. An EasyJet skipper living on London on two or three times the pay could manage a semi detatched house and a cleaning woman once a week.
If the foreigners are simply contract pilots employed for a fixed term then Garuda have to pay the going rate to compete with Vietnam/Korea/China etc
It would be reasonable to offer any local pilot who wants it, the same terms and conditions as the contract pilots. Fixed term with no guarantee of extension, first out the door in the event of a down turn, back of the queue for upgrade behind those on normal terms. In return they get the same pay.