Can I Whatsapp with my Indonesian SIM-card?

Yes, you can continue to Whatsapp with your Indonesian SIM card.

Whatsapp gives you the option to Whatsapp with your own number, even if you have an Indonesian SIM card in your phone.
This way you remain easily (and cheaply) accessible for your family and friends.

Make sure to change your sim-card at the airport on arrival. Here the can unblock your phone for the Indonesian network. It is difficult to find another place in the country where they can unblock your phone.