Srettha, whose Pheu Thai party leads the coalition, and 33 cabinet ministers pledged their loyalty to the monarchy during the ceremony at the Dusit Palace in Bangkok.

Srettha Thavisin will be tasked with forming and holding together a potentially fragile coalition that will include parties backed by the royalist military.

Hun Sen has said he would step down and hand over power to his son in August, ending a 38-year rule during which he established stability after years of war but stifled democracy in the process.

The vote for a prime minister can only be held after the Constitutional Court rules on an appeal by Move Forward against the thwarting of its bid to appoint a premier.

Hun Sen, who has ruled the Southeast Asian country for 38 years, was speaking just days after his ruling Cambodian People's Party swept a general election after running virtually unopposed.

Hipkins, who has refused to comment on his policies since being elected leader, will hold his first cabinet meeting on Wednesday.

The police and education minister will lead his party's uphill battle to win general elections on Oct 14 as the party lags in opinion polls, criticised by opponents over rising prices, poverty and crime rates.

Leadership hopefuls will gather when the centre-left Labour party caucus meets to elect a new leader, who will become prime minister.

The constitution and the Judicial Appointments Commission Act 2009 must be amended to remove the prime minister's role in this regard.

Haniff Khatri Abdulla says the suggestion will remain only an idea if action is not taken to amend the existing laws.

Rafique Rashid says the prime minister should concentrate on his work instead of entertaining criticism against him.

The Malaysian Bar says the appointment of judges should always be free from the influence of the executive.