J.
Google
Very good, although many of the texts are out of date, apparently written in the early 2000s (references to Playstation 2, events only going up to the late '90s).
I thought this museum was much better than the hilltribe museum in Chiang Mai, with much better English-language information, and more culturally sensitive and thought-provoking texts about the status of these minority groups in Thailand and relationship to tourism.
It's also nice of them to provide coffee/tea during the introductory video, and a woven bracelet with cost of admission.
The woman who was working front desk when I came was nice, though she disappeared for a bit, which was probably confusing to new visitors who came in.