Why do you just assume he is of a mind to go with working girls? Apart from this dowry incident his relationship with the Uni student appear to be perfectly normal and happy.
I think his "dilemma" is should I ditch her OR pay the dowry.
In my country a wedding costs about 1M baht anyway so if - as was said in the article - she gets half of it then he's only risking 500,000 baht which............if he loves her the way he says he does might be a risk worth taking.