Sex was violence, blood, bad smells and big troubles. In Thailand past and today, they do not teach that to children, they do not indoctrinate their population with creeds of sin and shame. Buddhism is a philosophy of acceptance of life. Christianity is a socio-political control perversion. Sex in Thailand is not something to be ashamed of.
Sex is like eating, breathing, shitting and sleeping.
It's just one of those things that your body has to do now and then. There are rules, there are social mores. But no Thai I've ever met has any perception of shame in sex. Long before Farangs arrived here the houses of comfort were doing a good trade. Father's took their young sons to be educated about life and sex.