"I'm sure many Australians feel the same and we'll do all within our power to suport them and get this young fella back home.''
Mr Rudd said the consul and the consul-general were having "rolling'' contact with the family.
A lawyer for the boy, Mohammad Rifan, said Lewis was "angry, crying'' and depressed.
He told AAP he could be charged under provisions for juveniles, in which case the maximum penalty would be six years.
Lewis was allegedly caught with 6.9 grams gross of marijuana, or 3.6 grams nett.
On holidays with his parents and staying in the luxury resort area of Legian, he was with a friend when he was arrested on Tuesday afternoon.
It's alleged he bought the marijuana for the equivalent of $A25 after being approached by a dealer while on his way to get a massage in Kuta earlier in the afternoon.
Police then detained him outside a supermarket after he left the place where he received the massage.
Under Indonesian law, there is no juvenile court system, so if he is charged the boy is likely to be placed in an adult prison.
He is the youngest Australian to be arrested in Indonesia.
- AAP