The boy, wearing a mask to protect his identity, arrived at Denpasar District Court with his mother for a brief, closed-door hearing.
Prosecutor I Gusti Putu Gede Atmaja later told reporters that the teen from Morisset Park, Australia, faces up to 12 years in prison if found guilty of buying 3.6 grams of marijuana on Oct. 4 while on vacation with his parents and a 13-year-old friend.
He said two community guards saw him pull the drugs out of his pockets after his arrest.
The boy's lawyer, Muhammad Rifan, said because he's a minor and appeared to have been purchasing the drug for personal use, not distribution, he could escape jail time.
Rifan said that in the best case scenario he would be allowed to return home in the custody of his parents.
The trial, being closely watched in Australia, continues Friday.
Dozens of Australian citizens have been thrown in jail or placed on death row for smuggling or possessing drugs in Indonesia. However, the boy -- who cannot be identified under Indonesia law -- reportedly is the youngest to go on trial on drug charges.
Indonesia has extremely strict drug laws and people who are convicted of smuggling or possessing drugs are often executed. More than 140 people are on death row, including more than 50 foreigners.