Interesting to see Malaysian registered vehicles in Indonesia! From what I've seen, foreign vehicles are required to put on an Indonesian temporary plate? Reminds me of requirements for foreign vehicles like HK entering China needing a separate plate.
Also on the other hand Indonesian vehicles do not need a temporary plate to enter Malaysia
Only small temporary license plates are attached to the front and rear windows. Like in this photo, you can see a patch that says the license plate number and validity period until January 10, 2024. Not under / above the plate like Hong Kong plates when entering China which requires a separate plate.