Bali prosecutors want an Australian man allegedly caught smoking a joint on the beach to serve up to 12 years in jail.

24-year-old Nicholas James Langan was arrested on January 27 at a beach in Canggu, north of Kuta, for smoking a marijuana joint.

Police seized the 0.1 gram joint and a small bag of marijuana weighing 0.86 grams.

Prosecutors have finalised the charges today, pushing for Langan to face a maximum 12 years jail for drug possession.