not a real risk. the skin on the thigh is thick and resistant to herpes infections.
What if he received a kiss on his inner thigh?
you can contract herpes from just skin on skin contact but the risk of such is very, very low.
you can contract herpes on your buttocks correct? So why is there almost no risk of herpes. If she had genital herpes and then rubbed on his butt wouldnt it be a possible herpes infection.
this is almost no risk for herpes transmission. no need for him to abstain from sex with his regular partner.
to best protect yourself and save yourself worry during erotic massages, make sure your under wear is on and so is the masseuses. it gives you a barrier, especially since often the masseuse might be tempted to take things further to get an extra buck or two.
grace