For anyone passing through and in need, there is now a gay massage joint in Surin named Heaven Spa. They can be reached via Line (ID: themist25) or via their Facebook page:
https://m.facebook.com/heavenspasurin/
The line-up seems to be largely made up of veterans from Bangkok massage parlors (Body Club, Hero, Albury) who enjoy the relative lack of competition in this part of the country.
1,400 for a one-hour oil massage, including minimum tip.