To avoid the great bulk of tourism sites with their inaccurate pop-history, use Google Scholar for searches on historical topics in Southeast Asia and Yunnan.
The article "UC Libraries Use of Google Scholar - August 2005" lists the ways that students and teachers in the University of California system find Google useful. Here are some important advantages:
1. It allows more effective key word searches because it searches full texts of journal articles and books not just abstracts.
2. Like Citeseer in the sciences you can search for "author references to particular named data sources, publications, or institutions."
3. Also good for subject areas where there is not much from specialized databases which is certainly true of Burmese history.
One of the top hits for Yunnan and Burma was this highly suspect history of Ming China in one web page. It talks over and over again of Lolo rebellions in Yunnan during the late fourteenth century which are actually ethnic Tai rebellions. It's unclear where the author is getting all this information because he doesn't cite any sources. Perhaps he is misinterpreting the ethnonym "Yi" which currently refers to a Tibeto-Burman ethnic group, but in Ming times also referred to Tai ethnic groups. The Ming invasion of Yunnan and the Tai reaction along the frontier is covered, of course, in great detail by Southeast Asia in the Ming Shi-lu.
There's also a weblog devoted to Google Scholar.