The BBC World Service operation will cover local and international news in Thai and English for an initial period of three months, the British broadcaster said, launching on Facebook at 6.30pm on Thursday.
The military rulers have suspended democracy since seizing power on May 22, imposing martial law, banning public rallies and censoring the media to stifle any dissent.
"One of the fundamental principles of the World Service is to bring impartial and accurate news and to countries when they lack it," Liliane Landor, head of language services at the BBC World Service, said in a statement.
"We think the time is right to trial a new Thai and English digital stream to bring trusted news and information to people inside Thailand."
National Council for Peace and Order spokesman Werachon Sukondhapatipak said he was happy to help the BBC "better understand the situation in Thailand".
"We don't have any problem as long as they don't send any provocative information that is negative or impacts the stability of the country," he said.
Last month the junta said it would set up five panels to monitor national and international news organisations as well as social media in its latest attempt to control the press.
The coup in Thailand follows years of political divisions between supporters of fugitive former prime minister Thaksin Shinawatra and a royalist establishment backed by parts of the military and judiciary.