He said if the National Reform Committee approved the new charter draft, tentatively scheduled for November, it would take three months to complete a public referendum on it.
If the charter were accepted by the public, it would be forwarded for Royal endorsement.
The Election Commission then has to prepare an organic law on the election of MPs and senators, which would take two months.
Somchai said there would have to be a gap of two to three month between the more complicated process of electing senators and the general election.
“It is possible that the election of MPs will be held at the end of April and then a senatorial election held two or three months later,’’ he said.
He voiced concern that the elections under the management of a new election body, with permanent officials as its members, may face political interference.
He said the Election Commission would meet today to discuss organising election simulations so the public understands the new election system.
Most people surveyed by the Political Development Council want the prime minister to be directly elected, the council’s president, Theerapat Serirangsan, said.
The survey was conducted from March 1-25 on 1,478 respondents from 55 provinces.
Seventy per cent of respondents believe a PM must be directly elected by the people to bring about sustainable democracy, while 11 per cent believe that can be achieved via a PM elected by MPs and senators.
Another 7.8 per cent and 7.5 per cent said that could be achieved through a PM elected by MPs and suitable people respectively.
Asked what is their most preferred election system, 37 per cent said a mix between constituency MPs and party-list MPs, 26 per cent said Germany’s mixed-party-list system, and 26 per cent preferred the constituency system.
Fifty-five per cent of respondents want senators directly elected by voters, 24 per cent want a mix of appointed and elected senators and 14 per cent would prefer to see senators elected in accordance with their professions.
Sixty-one per cent want a clear separation of power between the government and Parliament, meaning MPs and senators could nor hold ministerial posts.
Most want a government to serve a four-year term and no more than two consecutive terms, with the PM stepping down after two terms.