Expatriates living in Indonesia usually arrive with cover from somewhere else, then discover it behaves differently here. Three things are worth settling early.
You are likely required to join BPJS
Foreign nationals working in Indonesia for six months or more are generally required to participate in the national scheme, and employers typically arrange registration. Treat it as a legal base layer, not as your main health plan.
Local policy or international policy
A local Indonesian policy is cheaper, uses local hospital networks, and is written in Indonesian regulatory language. An international policy costs considerably more but travels with you, often covers treatment in Singapore or your home country, and continues if you move again.
The right answer depends on where you would actually want to be treated for something serious, and whether your employer's package already includes one.
Medical evacuation is a separate benefit
If you live outside Jakarta, Surabaya or Bali, the nearest hospital able to handle a complex emergency may be a flight away. Evacuation and repatriation cover is not automatic in every policy. Check whether it is included, what triggers it, and who decides.
Watch the ordinary details
Whether cover continues after you leave employment, whether your home country still counts as in-scope, how pre-existing conditions declared at underwriting are treated, and whether dependants on a family KITAS are included on the same terms.
And the part that applies to everyone
A serious illness abroad costs money and stops income at the same time. Working out that combined number is the same exercise for expats as for locals, only with larger hospital bills and fewer local support structures.