For him to be accepted at an Indonesian school, he had to become a citizen of Indonesia.
When you become a citizen of Indonesia you must renounce or apply to change the citizenship. There’s no proof that Obama did that.
You need to keep a few things in mind when thinking about the family in Indonesia.
The CIA was very involved in trying to overthrow Sukarno. At one point, they devised a fake honeytrap and enlisted a CIA cutout as well as Bing Crosby to get involved.
Lolo was a military officer studying in Hawaii.
The Ford Foundation was in Indonesia. Many believe that the Ford Foundation was involved with the CIA.
There is more involved here than a simple marriage between two people that move to Indonesia.
Obama may or may not have been an Indonesian citizen but they got him into school. This school was the same school of the boy who played with Obama - who was only one of two families in the whole country to have a certain car..the other being a gift to the President. Can’t remember the car. Maybe Cadillac.
Put become in quotes. Even if Indonesia required it, it doesn't mean that it really happened depending on how vigorously they checked the citizenship of a step-child of an Indonesian. Look how crappy our checks of citizenship are for cases where someone has to be a citizen or legal resident.
There’s no proof of anything; that’s the whole point!