- First things first, you have to get your hands on actual VPN software and configs. Many providers who are aware of VPN censorship and cater to these locales distribute their VPNs through hard-to-block channels and in obfuscated packages. S3 is a popular option but by no means the only one, and some VPN providers partner with local orgs who can figure out the safest and most efficient ways to distribute a VPN package in countries at risk of censorship or undergoing censorship.
- Once you've got the software, you should try to use it with an obfuscation layer.
Obfs4proxy is a popular tool here, and relies on a pre-shared key to make traffic look like nothing special. IIRC it also hides the VPN handshake. This isn't a perfectly secure model, but it's good enough to defeat most DPI setups.
Another option is Shapeshifter, from Operator (https://github.com/OperatorFoundation). Or, in general, anything that uses pluggable transports. While it's a niche technology, it's quite useful in your case.
In both cases, the VPN provider must provide support for these protocols.
- The toughest step long term is not getting caught using a VPN. By its nature, long-term statistical analysis will often reveal a VPN connection regardless of obfuscation and masking (and this approach can be cheaper to support than DPI by a state actor). I don't know the situation on the ground in Indonesia, so I won't speculate about what the best way to avoid this would be, long-term.
I will endorse Mullvad as a trustworthy and technically competent VPN provider in this niche (n.b., I do not work for them, nor have I worked for them; they were a competitor to my employer and we always respected their approach to the space).