Police later said the photos were doctored and kept the wife, who is Thai, in custody.
Andrew McGregor Marshall said in a statement that his wife, Noppawan “Ploy” Bunluesilp, was visiting Bangkok with their three-year-old son when both of them were taken by officers to a police station along with his father-in-law.
Armed with a search warrant, police also took computers and several items from the house. Police refused to say why she was detained or questioned.
Marshall tweeted photos on Thursday which were published in the German tabloid newspaper Bild and were purportedly of Crown Prince Maha Vajiralongkorn at an airport in Germany.
The crown prince spends much of his time in Germany.
Marshall, who used to be based in Bangkok, is a frequent critic of the Thai monarchy and the military government.
Under Thailand’s strict “lese majeste” laws, criticism of the monarchy is punishable by up to 15 years in prison.
Marshall and his wife have not lived in Thailand since 2011, but he continues to write about the country and is banned from entering it.
In the statement issued from Hong Kong, where he currently is, Marshall said Noppawan, 39, who used to work for Reuters and NBC, is currently not working.
“Ploy has never been involved in my journalism ... There is no reason for police to detain her. If Thai police believe that I have broken Thai law they should seek my extradition to Thailand via legitimate international legal challenges. It is unacceptable to harass an innocent woman simply because she is married to me,” said Marshall, who also used to work for Reuters.
Police Lieutenant General Thitiraj Nhongharnpitak told reporters she had been detained in connection with the photos that Marshall had posted on his social media, and which were “deemed inappropriate”.
Lt Gen Thitiraj said officers had determined that the photos are doctored, and that Marshall and two Thais, whom he did not name, are responsible for creating and posting fake photos on social media.
He did not say whether Marshall’s wife will be charged.
Marshall has confirmed that his wife has since been released following questioning.