This conflict of interest is partially right. But MAS being both a regulator and a central bank, MAS and MoF have to be able to work together. By and large this arrangement has worked very well, since MAS has managed regulatory policy well. I would also think that in the times that we live in amidst inflation and deflationary trends, where countries are following the beggar thy neighbour policy, and where easy monetary policy has become the norm, the choice of Tharman (given his long stint at MAS) as both Chairman and FM is a very good decision.
Being appointed both MAS Chairman and Minister of Finance is already a glaring conflict of interest.