What part of the city are you staying in? When are you coming? If staying in CBD this is one of the nicer spas for gay men in JKT:
http://www.9massage.com/
If you are staying in South JKT, I can recommend another one. If you are coming soon, it is Ramadan; don't expect much to "happen" before the sun goes down. Some bars/clubs/massage may be closed for the month. Feel free to PM me if you have any further questions about gay jkt.