Like every other record that’s missing in Obama’s life, there are no records of him renouncing his foreign citizenships.
He renounced his citizenship in Kenya and Indonesia simply by not living in the country for a certain number of years.
Indonesia, from what I've read, does not allow dual citizenship so he would have had to formally reclaim his US citizenship on turning 18 IIRC. Apparently there was never a formal request to regain his US citizenship.
So apparently he isn't a citizen of any country.