I cannot answer why Thailand has the death sentence. I would ask this same question if I met a Thai politician. I don't understand it. It is not part of the Buddhist religion, but like so many countries around the world they try to separate religion from the government, Germany, America, Australia all try to do, they try not to have religion interfere with how they make laws and such. So I cannot answer why any Buddhist would vote for that. What does Buddhism say about capital punishment? - As far as the death sentence is concerned that should absolutely not be done, because it is killing. It is as simple as that.