I would just finish the massage by planting a huge kiss on his bumIf you get lucky enough to be allocated as his therapist next time he comes in, just make obvious small talk to let him know you're single (and find out if he is!). Humour is the best way.
You could tell him you've got a special on "extra's" this month, that they're free! Lol. Just kidding!!!!
Don't anyone jump down my throat please. IT WAS A jOKE!