I think many of them are actually on 2-month contracts (with perhaps a “gentleman’s agreement” that they stay a year) so the bonus is paid pro-rata bi-monthly – I know guys in Jakarta and Bandung with this arrangement. This is perhaps in case they’re unable to complete the year (due to circumstances beyond anyone’s control, if you know what I mean) they don’t lose out financially. The teachers on the yearly contracts get their bonuses as normal, so, yes, in their cases they do act as an incentive to complete the contract. Who knows, it’s all a bit of a rigmarole isn’t it?

Sorry OP, gone off topic a bit there!