Are there any hiking or walking trails in the mountains near Hang Dong?

I believe there are at the HUAY TUNG TAO resort, north of Chiang Mai on the 107 to Mae Rim. (left hand side or the road heading north). There is, apparently a 7km circular trek with a waterfall and views.

There is an entrance fee to get into the lake complex.

Thanks but hoped to find something south west of Chiang Mai .

You could do some hiking around Op Kahn National Park. http://www.dnp.go.th/parkreserve/asp/style1/location.asp

http://www.opencyclemap.org

Shows some of the trails.

Ob Khan NP.