The schoolboy was arrested on October 4 after he was caught with 3.6 grams of marijuana when police swooped on him and a 13-year-old friend after they emerged from a massage salon in Kuta.
It was initially thought that with time already served taken into account, the teenager would not be released until December 4.
However, Atmaja said on Wednesday it was possible the boy could be released as early as Friday, two days earlier than expected.
"After we report this, on Friday, we will execute the sentence,'' he said.
"After the execution, on when he's to be released, then it's prison's authority.''
The boy's lawyer, Mohammad Rifan, said last week he was also unlikely to appeal as doing so would have seen the teenager forced to stay in Bali beyond when his sentence was due to end.
An appeal may also have resulted in a longer sentence.
"We are accepting,'' he said on Wednesday. "The decision is the parents' request. If we go for appeal, there's a chance that the sentence would go longer.''
- AAP