bali prosecutors want an australian man allegedly caught smoking a joint on the beach to serve up to 12 years in jail .
nicholas james langan , 24 , from townsville , was arrested about 1.00 am on january 27 at a beach in canggu , north of kuta .
police allege he was smoking a joint at the time of the arrest .
prosecutors said he possessed a small bag of marijuana weighing 0.86 grams .