My understanding is that Western law usually applies to children in Thailand fathered by Western men. That is, if a Western man gets a Thai woman pregnant the Thai woman living in Thailand can have him 'traced' in his home country and made to pay her alimony even if she is in Thailand and he is in his home country.
I am wondering when Thai men father children with Thai women in Thailand is there Thai law that can make the Thai man pay for the child?