Defo no sleeping bag. If you find you need one in some places they are easy to pick up, but most hostels won't let you use your own anyway, esp in Oz. I took a sleeping bag liner, and when I lost that, I just bought an extra big sarong which doubled up as a beach mat, blanket on the buses etc. Try and bring stuff and that can be used as a few different things. It will be too hot in most places around Asia anyway so total waste of time to bring the sleeping bag.