The Criminal Court will deliver its verdict on Somyos Prueksakasemsuk's lese majeste case on Jan 23.
The court set the verdict date yesterday after reading a Constitution Court ruling which dismissed a petition filed in May by Mr Somyos and a second lese majeste defendant against part of the Criminal Code under which they were charged.
The pair argued that Section 112 of the code, which covers lese majeste offences, violated their right to freedom of expression.
In their ruling delivered yesterday, however, the Constitution Court judges upheld Section 112, saying it protects the king, as the head of Thailand, from threats and defamation.
The section seeks to maintain public order and good morals in accordance with the rule of law, they said.
More than 100 people attended the court session in which the ruling was delivered _ including representatives from several European embassies, NGOs and Mr Somyos's wife and son.
After the ruling, Mr Somyos insisted the lese majeste law undermines the justice system and compromises the integrity of the monarchy.
He criticised parliament and the government for failing to heed calls to amend it. The Committee to Campaign for the Amendment of the Article 112 has been lobbying to amend the section.
Failing to change the charter compromised the institution of the monarchy and eroded social justice, Mr Somyos said.
"It's a pity that Prime Minister Yingluck Shinawatra does not dare to take a lead in this case," he said. "Her cowardice and indecisiveness makes her no different from other dictators."
Mr Somyos was charged with committing lese majeste by publishing two articles written by another person in the Voice of Taksin magazine, of which he was the editor.
He was arrested on April 30, 2011, five days after he launched a campaign to collect 10,000 signatures required for a parliamentary review of the lese majeste law. His applications for a temporary release have been repeatedly turned down by the court.
The UN Working Group on Arbitrary Detention has ruled Mr Somyos' pre-trial detention for the past 20 months violated international human rights laws and standards.