Indonesia is also very corrupt (111th out of 180 in Transparency International's index, and I have encountered the police corruption there first-hand). I wonder whether the corruption might be so bad that people wouldn't report murder to the police, and so the official statistic might be lower than it should be?

The former anti-corruption chief of Indonesia was jailed earlier this year for conspiracy to murder. I could imagine that if he's not the only government official organizing murders, then that might not reliably be reported to the police.

(This is poorly-informed speculation and I wouldn't be surprised if some knowledgeable person writes a scathing correction. Better information would be appreciated.)

At one time it was compulsory for all Indonesians to officially have a religion. Is it still so? I believe the reason was opposition to Communism by the Indonesian government.

That's a good point. Interestingly, that religion is Muslim. But if we compare countries with similar GDP the U.S. is put to shame. Even Germany beats us for being less violent, and less religious.