Not necessarily. It would mean that his step father would have surrendered his citizenship on his behalf. If, after the age of 18, he had taken no positive actions to affirm Indonesian citizenship, then his U.S. citizenship would revert to its original character.
That's why Obama's mysterious scholastic days are so critical. If he used his Indonesian citizenship to gain entrance to either Occidental or to Columbia, then he very likely renounced his U.S. citizenship as a consequence. If he didn't do this, then he's probably home free.
Only the Shadow knows.
There are some weird things about his mother’s passport applications..including different years and places for her marriage to Lolo..and another last name for Obama.
I think the chances are good that he attended college as a foreign student..and this is one of the reasons things are locked up.
The passport application weirdness is in line with my theory that the family worked with the Spooks...and this is why things are locked up never to be seen by the public.