The answer to Mr Koh Twitter is simply both Indonesian Navy and Coast Guard don't have adequete budget to keep their presence 24/7 in Natuna Sea. While Chinese Coast Guard have enough resources to keep close to perpetual presences there.
Chine coast guards and fisheries can maintain continues presences around their "civilian" fishing boats fleets. While many SEA fishing boats (whether Indonesian, Vietnamese, Malaysian or Philipines) can not hope that around the clock coverage from their own respectives naval fleets.
There're rumours on the idea of sharing securities resources among ASEAN members bordering SCS. However this will complicate matters of sharing jurisdictions (something that's still "no-no" among ASEAN members) and more importantly open the door for ASEAN joint securities arrangement. Which in turn just a bit too close on securities pact. Thus it is too sensitives for ASEAN basic principle that still avoiding that area.
For Indonesia, to me this is shown more OPV's for Navy and Coast Guards plus accompanies enough operating budgets is more important then fancy frigattes. Unless the respectives present and futures administrations and their respectives political parties in parliement, can commit for more defense and securities budgets (investment and operational).
Something that I don't see the Indonesian political establisments can have enough guts to commit for substantial invesment on the area, in foreseable future. Yes they can talk on increasing invrstment and operations. However mostly for images building, and to follow that with enough money trails commitment, that's another stories.
So beggar can't choose. Build more Patrol boats and OPV's for more presences. It is cheaper in Investments and more importantly cheaper to operate. However it will not be 'sexy' projects, which god knows Indonesian Bureacracies and Political establishment are like image buildings, sexy and fat projects.