Bill should be put forward in a referendum

Justice Minister Chaikasem Nitisiri said the legislation
of an amnesty bill should be under the purview of lawmakers, who receive their mandate through elections. He also said he himself is in favour of such a move.
I have some questions:
First, the present constitution was approved by the Thai people through a referendum. If the Pheu Thai party sees a need to have it altered, why not put its request through a public referendum first?
Second, Mr Chaikasem claims that members of parliament represent all the Thai people. That is only partly right. Pheu Thai party won less than 20 million votes in 2011. That was less than one-third of Thailand’s population. How can Pheu Thai claim to represent the will of all of us?
Third, even the relatives of the victims of the 2010 violence came out to denounce this bill as unfair. How can you explain your own motives for this charter change?