There are "chains" of genuine massage places in Bangkok - Marble House is one although I think it has recently changed its name. There's a lane to the left off Suriwong Rd just before you get to Patpong which has nothing else but places where you get the genuine article - around USD10 for 2 hours and you should give the massesuse a tip of USD2 or USD3 at the end. It's mostly women but you will find some young men and also some blind men in some of those places. You can ask for a man - they will not be offended nor assume anything other than you prefer a male masseur. I would say that 99.999999% of the time there will never be the slightest suggestion of anything else and my guess is that if you ask they may request that you leave

Only once in my 20 years of going to that area for my twice-weekly massage have I ever had the slighest sexual advance, which happened when I went to a place other than my usual, I was in an area by myself and the woman rested her hand on my groin. I moved it away and nothing more was said. I usually have the same woman every time, although occasionally I have another is she is not available. They all have numbers, so assuming you asked the first time (they don't necessarily wear their number) next time you can say "No. 8?" and you will get him/her, if available

My regular did suggest once that we get married!!