Hi Smart Sexy Tiler. You are correct. Do not confuse this place with Smart Beach on Ratchadaphisek. I thought you had been to The Mall, Bangkhe...also on the route of 547 but much further out. I thought I would never read you saying(or hear you reading?) that "....I suspect, is better gained by taxi than by 'bus.?". 547 or 163 or 15(often free) all go door to door from Silom.
They used to have a web page with all the boys' photos at
www.smartbankspa.com but it doesn't work no more, no more! But the place is still operating. Just go and look...they won't mind if you say, "Ok, thanks, I don't have time now but I'll return Tuesday" or some such get-out/excuse.
There is also a similar, but greedier place called Bandung spa across the river...near the Rama 9 bridge/Kasikorn Bank HQ. It can be very off-putting but some boys can be good...but definitely don't commit to anything unless you have completed an exhaustive search or what they are offering. I did find and enjoy a great boy there once.