The military has sought to stifle criticism as it consolidates power after toppling an elected government on May 22, detaining politicians and restricting print, radio and broadcast media.
But authorities have struggled to control activity online, where users have used social media to organise protests and express opposition to the coup. The junta has warned about the spread of what it considers provocative material on social media, and asked service providers to help tighten censorship.
"We want to talk to them informally," Pisit Pao-In, adviser to the permanent secretary of the Information and Communication Technology (ICT) Ministry, told a news conference on Thursday. "We do not ask them to install any additional software. We just ask them to help filtering content."
Officials would have to travel as the three companies had no representatives in Thailand with whom to hold talks, he said, speaking after a meeting in Bangkok with Internet gateway and Internet service providers (ISPs).
The ministry asked ISPs to block websites within an hour of receiving an official request to take them down, said an ISP source who attended the meeting on Thursday, declining to be identified because he was not authorised by his company to speak to media.
After the coup, the ICT established a commission to monitor websites and block content that flouts military guidelines or Thailand's strict Lese Majeste laws. There are three monitoring centres working 24 hours a day: one at the army, the ICT and the state telecom regulator, Pisit said.
More than 100 web pages have been blocked since the coup, he added. The ICT, the police, the intelligence agency and regulator work together to monitor websites, he said.
Thai users were alarmed on Wednesday when the ministry blocked access to Facebook. It is unclear why the site was blocked.
The government had no plans to block access to Thailand's 24 million Facebook users, Pisit said.
Norwegian telecoms group Telenor, which owns a controlling stake in Thailand's second-largest mobile operator, Total Access Communications, said the outage had lasted 55 minutes.
"Telenor Group believes in open communication and regrets the consequences this might have had for the people of Thailand," the company said in a statement.
The military plans to consolidate the 15 private and state-run Internet gateways into one single national gateway to facilitate monitoring.
"We will have a single gateway to monitor inflow and outflow of content on the Internet... The main reason is for security," Pisit told Reuters. He said it was unlikely the gateway would be completed before the end of the year.
The single gateway would give the government increased control over access to websites hosted outside Thailand, the ISP source said.
Thailand has 15 Internet gateway providers and leading players include two state-owned firms CAT Telecom and TOT Pcl and private company True Internet, part of True Corp.
© Thomson Reuters 2014