Yes, you can.
If your KITAS is sponsored by your own PMA company, you are still allowed to invest in another company in Indonesia — as long as your role in the other company is limited to being a silent (passive) shareholder.
This means:
- you cannot hold an operational or managerial role in the second company,
- you cannot perform work activities there without a proper work permit,
- your active employment must remain tied to the company that sponsors your KITAS.
Passive investment is allowed, but active involvement requires the correct visa and permits.