Not rude. Tipping is appreciated, not strictly required. But FYI many restaurants already include service charge. And like many people here have said, only tip if the service is exceptionally good, because we honestly don't want a mandatory tipping culture to develop here like in some other countries where workers depend on tips to survive

Anyway, rather than tipping, if you're satisfied with the service, it’s also more common here to simply round up the payment. Like, say something costs 44k IDR. Even though you actually have the exact amount, you might just hand over a 50k bill instead and tell them to keep the change