Digital Economy and Society Minister Buddhipongse Punnakanta has told owners of coffee shops with WiFi to turn over their customers' browsing histories for the last 90 days.
The minister told reporters that the search data will be used to track down "fake news" that could cause rifts and disunity in society.
The so-called anti-fake-news centre, formed in August, would use the data to monitor and investigate those who disseminate inappropriate information online in violation of Section 26 of the Computer Crimes Act, he added.
Mr Buddhipongse said owners of coffee shops may not realise that the law dictates they must collect their WiFi log files.
These record either events that occur in an operating system or software, or messages between different users of communication software.
The measure is not meant to track down customers or abuse personal data, he said, but instead to help prevent abuses via internet platforms.
"Some people are likely to access the internet via WiFi in coffee shops to commit offences because they think that no log file is collected," Mr Buddhipongse said.
In August, the ministry appointed four subcommittees under the anti-fake-news centre to deal with four topics it says are most frequently abused by the dissemination of fake or fraudulent information.
Those topics are natural disasters, the economy (including finance and capital markets), public health, and state policy and security.
Mr Buddhipongse made the announcement at the Technology Crime Suppression Division (TCSD) during a press conference on the arrest of a 25-year-old man for "inappropriate tweets" under strict cyber laws now administered by his ministry.
Authorities have arrested and charged political activist Kan Pongpraphapan for posting "inappropriate" content online, cyber police at the TCSD said yesterday.
Mr Kan's lawyer Winyat Chatmontri denied reports that his client had criticised the royal family.
Mr Kan was detained on Monday night at his home in Bangkok's Phayathai district and questioned over a Facebook post, described by police only as a story about the history of a foreign country.
The suspect was not charged with lese majeste but with violating computer crime laws involving national security, police said. They referred obliquely to the #royalmotorcade hashtag in announcing the arrest.
"The comments Mr Kan posted on Facebook did not mention Thailand's monarchy nor the #royalmotorcade hashtag at all," Mr Winyat insisted.
"His post was about the history of Russia, France and Germany. But the charge brought by the digital economy ministry resulted from an interpretation and an effort to link him to the hashtag," Mr Winyat said, according to Reuters.
Speaking briefly to the media while being transferred at 3am from the TCSD to the police station, Mr Kan said he was determined to fight the "serious charge".
He was released on bail with a surety of 100,000 baht.
Prior to Mr Kan's arrest, the Ministry of Digital Economy and Society had alerted the TCSD to his alleged misconduct, said the lawyer, adding that Mr Kan's Facebook post of only five lines was doctored and then circulated on Twitter, leading to his arrest.
Pol Col Siriwat Dipho, deputy commissioner of the TCSD, said the suspect denied any wrongdoing. If found guilty, Mr Kan faces up to five years in prison and a fine of 100,000 baht, while those who share his Facebook post will face an equal penalty, said Pol Col Siriwat.
Meanwhile, Deputy Prime Minister Prawit Wongsuwon said yesterday that four to five other people were involved in the alleged violation of the Computer Crime Act that led to Mr Kan's arrest.