The whole set up means there will never be a new democratic government here in Thailand, you are going to need 376 to win if 750 voters. Take out the 250 disgustingly put in senators and you only need 126 of the opposition to block any candidate. Which basically means a small opposition of say 130 can block any new PM until the next election
There should be a vote - first with the 250 senators. No PM then the military appointed are removed from the vote. OR the senators can stay in place but they cannot vote on new PM, but can block his policies (hate it, but its a compromise)