The most popular internet provider in Indonesia is Telkomsel. While the 4G SIM cards from this provider may be expensive, they offer the highest network speed.
Telkomsel offers prepaid internet packages like Kartu As, Kartu Halo, and SimPati. It's advisable to choose the SimPati package, which offers 4GB for 140,000Rp (~198,000đ) and 8GB for 170,000Rp (~240,000đ).
In Indonesia, you need to provide passport information to activate a SIM card.
To purchase a 3G/4G SIM card, you can pre-order on websites like KLOOK, KKDay, and collect it at Ngurah Rai Airport. Alternatively, you can buy directly at service counters at the airport or from authorized SIM card vendors on Bali island.