Prime Minister Prayut Chan-o-cha insisted on Thursday the monarchy needs the lese majeste law to legally protect the institution.
Gen Prayut said Section 112 of the Criminal Code for lese majeste acts must stand as the King is not in a position to defend or explain himself in legal situations as an ordinary citizen could.
"If His Majesty can't defend himself, we have to take care of him," the premier said, adding Section 112 has to be maintained.
Gen Prayut made his remarks after it was reported that former Pheu Thai Party leader Charupong Ruangsuwan had set up a non-governmental organisation called the Organisation of Free Thais for Human Rights and Democracy in the US. The group was set up in June this year. Mr Charupong, who fled Thailand post-coup, has been charged with violating Section 112.
Gen Prayut said the King's daily life is compromised by his obligations, and while foreign countries may criticise Section 112 from a human rights perspective because they do not understand the law, Thailand's unique situation makes protecting the monarchy crucial.
On Wednesday, Mr Charupong's Facebook page displayed a message entitled Serithai Prab Kabot 2014, or "Free Thais Suppressing Rebels 2014", announcing the legal registration of the Organisation of Free Thais with the US authorities after a lengthy process.
Mr Charupong, the NGO's secretary-general, announced the organisation was established to work on human rights issues and promote democracy.
It targets the military government through its anti-coup stance and demands that the government relinquish power and return the country to democratic rule.
After the coup, Mr Charupong failed to report himself to the National Council for Peace and Order.
The former Pheu Thai MP also accused Gen Prayut of working together with the People's Democratic Reform Committee to overthrow the Yingluck Shinawatra administration.