While I was thieving from Dorgesh-Kaan chests, I decided to also fix lamps at the same time and I found two more normal chests that are not labeled on your Dorgesh-Kaan map. They are both on the ground floor. One of them is in the room next to Ur-meg's room. Almost directly east of there, there is a cluster of three rooms and the other one is in the northern room.