The verdict came despite repeated calls by rights groups to free Somyot Pruksakasemsuk, who has been jailed since 2011.
It also underscored the harsh nature of Thailand's "lese majeste" laws, which have been criticised as a violation of free speech.
The articles were published under pseudonyms in Somyot's now-defunct Voice of Taksin magazine, which he launched in 2009 to compile political news and anti-establishment articles.
Judges found both articles contained content that defamed the royal family and argued Somyot, as a veteran editor, knew and chose to print anyway. He was given two five-year jail terms – one for each story. Somyot said he would appeal against the verdict but would not seek a royal pardon.
Somyot's articles were published in 2010, but he was arrested the following year after launching a petition drive to revoke Article 112 of the nation's criminal code, which mandates three to 15 years in jail for "whoever defames, insults or threatens the king, the queen, the heir to the throne or the regent".
A spokesmand for Human Rights Watch said "The courts seem to have adopted the role of chief protector of the monarchy at the expense of free expression rights,"