Kittiton Yaemsamai, 50, known among netizens as Kenji, was sentenced to 10 years for posting two electronic messages deemed defamatory to the royal family in August this year.
He was also sentenced to three years and four months for possessing an electronic document with lese majeste remarks showing "an attempt to defame, insult and threaten the King, the Queen, the Heir-Apparent and the Regent".
The Criminal Court at Ratchadaphisek then halved the prison terms, because he confessed, to five years and to 20 months respectively - a total of six years and eight months.
Kittiton, father of two children, was arrested at his rented house in Samut Prakarn on Aug 30 this year. He confessed during the police investigation and before the court in November without a further hearing or trial.
His lawyer, Anon Nampa, said the "attempt" charge is a new dimension of lese majeste application.
"Subsequently, just possessing a computer with alleged lese majeste remarks not yet disseminated is expanding interpretation of the law in an unprecedented way," said Mr Anon.
His client had chosen to confess, so there was no point arguing about the Criminal Code's article 80 concerning the factors leading to the committing of a crime.
Kittiton's 38-year-old wife of seven years said her husband's heart and interests are in supporting the course of justice for his red-shirt colleagues.
"As an orphan, he doesn't have a family of his own. Once, he lived with Khun Samak (Sundaravej) and he was so grateful to him. When the former prime minister died he was crying for him," she said.
She said sometimes she had asked him to be less involved, "but I know he's very sympathetic to the red-shirts, many of them are just poor and lacking opportunities".
With the family's bread winner behind bars, they had been kicked out of their rented house. Recently, the United Front for Democracy Against Dictatorship has provided some money to help their children.
Kittiton told the Bangkok Post through the bars of his court cell that he did not regret that his court case took place during the term of the government he helped voted into office.
"If I'm out for the next elections, I'll still vote for this party," he said.