The law provides: "Whenever no provision under this Constitution is applicable to any case, it shall be decided in accordance with the constitutional practice in the democratic regime of government with the King as Head of the State."
While the wording of the law is unclear, it is commonly understood that the clause is meant to be the last resort: Asking for His Majesty the King to appoint a prime minister at his discretion.
The former attorney general claimed if caretaker Prime Minister Yingluck Shinawatra was removed from office by a legal ruling, there would be no other way to get a new premier, given the circumstances.
But he stressed this was his own idea as a lawyer and the government might not necessarily approve of it.
"For months, there have been attempts to get a PM through this provision without prerequisites to do so. But if the day really comes when the PM must go, we may have to invoke it," Mr Chaikasem said.
Pheu Thai party spokesman Prompong Nopparit said later the party did not agree with Mr Chaikasem.
It remains convinced the solution is for the Election Commission to hold a new election as soon as possible.
Akanat Prompan, spokesman of the People's Democratic Reform Committee (PDRC), said Mr Chaikasem had surprised him because the government had always been against the idea, which had been championed by the PDRC all along.
But this only proves what the anti-government protesters have always wanted to achieve is constitutional.
"When the ruling is handed down, people will come in support of us while the government will incite its own supporters. Then, I am convinced government officials will come out to fight shoulder to shoulder with the people to defend rule of law," he said.
Virat Kallaysiri, chief legal adviser of the Democrat Party, slammed the idea as highly inappropriate because His Majesty was above politics and there was a constitutional procedure that could be followed.
He pointed out the difference between the procedure proposed by Mr Chaikasem and that of PDRC chief Suthep Thaugsuban was that the PDRC would propose a name to His Majesty only when an agreement had been reached among all related institutions.
The prerogative to propose the name lies with the House speaker, Mr Virat said, but since there is no House at the moment, the closest there is is the Senate speaker.
If Ms Yingluck is removed, she and her Cabinet will have no prerogative to do this, he added.
Mr Virat believes the government will try to mobilise people and instigate violence so a coup is inevitable, leading to the formation of a government in exile.