He was referring to a report that some NLA members planned to nominate the National Council for Peace and Order (NCPO) chairman as the next premier after a royal command is issued to formally appoint the NLA's president and two deputies.
Mr Srisuwan said the nomination of Gen Prayuth might contravene several sections of the 2014 interim constitution.
Sections 6 and 10 of the interim consitution, he said. stipulate that the NCPO chief is to give recommendations to His Majesty the King and countersign royal commands made accordingly. But if the NCPO proposes Gen Prayuth, its chairman, for prime minister, the practice might be seen as a collaboration which contravenes the Prime Minister's regulations of 2008, para 6 (4), concerning ethics of holders of political positions - it might also go against the fine traditions and culture of the country's administration under the monarchy as stipulated in Section 5 of the interim constitution.
Section 19 of the 2014 interim constitution allows the NCPO to propose through the NLA the removal of the prime minister. If the NCPO chairman and the prime minister are the same person, it would be awkward for that person to propose that he remove himself. The practice would go against the "checks and balances" principle.
Moreover, even after the prime minister and cabinet have been put in place to administer the country, the NCPO chief still retains the power to override all legislative, administrative and judicial orders.
Mr Srisuwan questioned how this power could be properly exercised if the NCPO chief and the prime minister are the same person.
He called on the NLA not to approve the nomination of Gen Prayuth for prime minister unless he resigns as NCPO chairman.