I used the Lowepro CompuRover AW a few times to my last ChiangRai trip. If you don't mind the total weight you have to carry, I would have to recommend this bag. It is avail in shops like TK Foto or AP in SL
http://www.lowepro.com/Products/Backpacks/notebook_camera/CompuRover_AW.aspx
http://www.lowepro.com/Products/Backpacks/notebook_camera/CompuRover_AW.aspx