Sponsorship letter for social visa

There's a least one poster here that deals with immigration issues as a professional.
I have no idea if he's any good or what sort of prices he charges, but a quick look at the Indonesia forum home page finds a lot of threads about immigration issues.
Send him a PM and see what happens.

The KITAS you need should cost around Rp 1 million or so, but agent fees vary. Their charges tend to be based on the paperwork, the fact they're responsible for your conduct whilst you're in Indonesia, and (more often than it should happen) how much they can screw out of you.
Working online probably requires a work permit but who would ever know and, as you're bringing cash into Indonesia without taking work from an Indonesian, who is likely to care?
Immigration are far from stupid so keep your mouth closed and they'll probably decide not to show any interest, even if they know.

Probably a silly thing to consider, is your internet connection, internet in Indonesia in general compared to the USA and Europe is below average at best but has improved but has a way to go yet and many places you can't even get a phone signal, larger populated places you “may” be ok

The above internet issues used to be true everywhere but many areas are as good as or better than the UK now.
My home connection and my phone internet access are both better than my sister's.
However, many places still have less than perfect internet so it's worth checking before you move to any given town.

Just tested my phone.
13 down
4 up

Easily fine for me but the OP may need more.
My home internet varies but is generally around 30 to 35 download

My phone and home are fine If I visit lampung area sometimes an issue Bengkulu a nightmare