That's the $64,000 question.
No one knows the answer.
And especially important is the question of whether he was still an Indonesian citizen, with an Indonesian passport, when he travelled to Pakistan, in 1981, as a 19- or 20-year old adult [remember, Indonesia did NOT recognize dual citizenship]:
Obama Citizenship Controversy - Did Obama Travel to Pakistan on an Indonesian Passport? A Summary.
http://www.freerepublic.com/focus/news/2059717/posts
true, indonesia only gives passports to its citizens like the US
Another question about the passport. If he did travel on an Indonesian passport, when was it renewed? Who renewed it? He was 10 when he was sent to live with the grandparents. At that time, which passport did he have? What name was on it?