If the guy is British you can't just get a brand spanking passport from the British Embassy if you say you've lost it / stolen.
Those days are long gone and the British Embassey is a far cry from what it was 10 years ago i'm afraid.
You get a transit passport or somesuch which means you have to return home and get another one done manually from the UK.
Ranong has a small detention center.
A barnpot Brit I knew on Koh Tao kicked up a real shitstorm at Ranong immigration one time ( he'd misunderstood his tourist visa dates and was overstayed). He got very aggressive and started spitting on the floor and was subsequently pounced on and carried away to the monkey bus and driven away to jail
LOLHe was detained for about 3 days until he had cooled his heels and paid his dues for the overstay.
