His Royal Highness Crown Prince Maha Vajiralongkorn wants at least one year to elapse before his coronation, Deputy Prime Minister Wissanu Krea-ngam has revealed.

However, Mr Wissanu said the parliamentary process to invite the heir to be king under the interim charter can proceed sooner.

Mr Wissanu said yesterday that Prime Minister Prayut Chan-o-cha had an audience with the Crown Prince to seek advice on how long the royal funeral ceremony for His Majesty the King should be.

The Crown Prince advised that royal funeral rites should continue for at least one year before the cremation ceremony is held.

"The Crown Prince told the prime minister that he would like everything to remain the same as when His Majesty the King was still alive, at least for now," Mr Wissanu said.

"He suggested not to let it be felt that the country is being left in a void. Don't let everything fade into the past too fast."

It has become clear that the royal funeral rites will last at least one year, which corresponds with the one-year mourning period for the public announced by the government, Mr Wissanu said.

"[After one year] other matters will be discussed such as the official schedule for the royal cremation and the coronation of the new king," he said.

Mr Wissanu stressed that the process to invite the Crown Prince, who is the heir to the throne, to become the new king is a separate matter from the coronation.

The invitation process by parliament, stipulated under the charter, is intended to ensure that continuity of the royal lineage is uninterrupted, whereas the coronation involves royal protocols for the heir to be officially crowned king.

The Crown Prince previously told the prime minister that he wanted to join the Thai people in mourning the passing of his father before he accepted the invitation to become the new king.

In light of this development, the government had not yet informed the National Legislative Assembly chairman about the heir.

According to Mr Wissanu, the title of "Somdet Phrachao Yu Hua" will be assumed for the new king before the coronation and the title of "Phrabat Somdet Phrachao Yu Hua" will be assumed at the coronation.

He confirmed that Privy Council president Prem Tinsulanonda has automatically assumed the role as regent pro tempore under a charter provision.

Mr Wissanu said the Privy Council will choose a new president now that Gen Prem has become the regent. The regent cannot concurrently serve as the Privy Council president.

The move is in line with Section 24 of the 2007 constitution. Although the 2007 charter was abrogated by the 2014 coup, its sections on the king are retained and remain in effect under the 2014 interim charter.

Gen Prem became the regent without the need for nomination during the transition to the new reign as stipulated in Section 24.

"When the regent is relieved of duty, he will be reinstated as president of the Privy Council automatically without the need for a royal appointment," Mr Wissanu explained.

Responding to a question about who would sign the new constitution, Mr Wissanu said the regent has the authority to endorse the new constitution. He said past constitutions were also signed by regents.

Mr Wissanu also dismissed rumours that the regent had the power to nominate the new king as he sees fit.

The royal succession must comply with the 1924 Palace Law on Succession, he said.

The law had been part of the 1991, 1997 and 2007 constitutions as well as the 2014 interim charter, and this same law has also been included in the new constitution that will be enacted shortly, Mr Wissanu said.

He said His Majesty had appointed his heir, the Crown Prince, on Dec 28, 1972, so there is no question as to who is going to be the new king.

According to the 2014 charter, when the throne becomes vacant and the king has already appointed his heir under the 1924 Palace Law on Succession, the cabinet notifies the parliament president, who convenes parliament to acknowledge the heir.

The parliament president then invites the heir to ascend to the throne.

In this case, the National Legislative Assembly will act as the parliament as there is no House of Representatives or Senate at the moment.