I've travelled quite extensively around the far east and stayed in some really dodgy hotels where you wouldn't trust the safety deposit boxes.
What I bought a few years back was a PACSAFE TRAVELSAFE
http://www.pac-safe.com/www/index.php?_room=3&_action=detail&id=18
It has been brilliant, it's a small pouch that's made of metal reinforced material that you connect and lock onto something irremovable such as plumbing.
I think I paid around £15 for mine and you can often see them on Ebay
Just a suggestion
Rog