Thailand’s junta leader, Prayuth Chan-ocha, has said he will “probably just execute” any journalist who does not “report the truth”.

Last month Gen Prayuth said he had the power to shut down news outlets, and on Wednesday he took an even harsher line. “We’ll probably just execute them,” said Prayuth, without a trace of a smile, when asked by reporters how the government would deal with those who do not adhere to the official line.

“You don’t have to support the government, but you should report the truth,” the former army chief said, telling reporters to write in a way that bolsters national reconciliation in the kingdom.

Prayuth, who is also prime minister, heads the ruling junta, the National Council for Peace and Order. He toppled the government of Prime Minister Yingluck Shinawatra in a coup last May, following months of mass protests aimed at ousting Yingluck.

Known for his abrupt manner and impulsive remarks, Prayuth launched a crackdown on dissenters after seizing power in May. He has said Thailand is not ready to lift martial law, which gives the army sweeping powers, including for arrest and detention. In January, the junta forced a German foundation to cancel a forum on press freedom, saying Thailand was at a sensitive juncture.

Since taking power, the junta has made full use of martial law, which also bans all political gatherings.

Prayuth was particularly critical of the Thai-language daily newspaper Matichon, accusing it of siding with the ousted former prime minister Thaksin Shinawatra and his allies. “Don’t think I don’t know that your writing is pro the previous administration,” he told a Matichon reporter shortly before boarding a plane to Brunei. “The previous interior ministry bought many advertising spaces from you.”

Since the army toppled Thaksin, Yingluck’s brother, in a previous coup in 2006, Thailand has been sharply divided. Thaksin’s support comes largely from the rural and urban working class, but the traditional establishment in the capital and the south loathes Thaksin and accuses him of nepotism, cronyism and republican leanings – accusations that he denies.

Shortly after taking power, Prayuth launched a year-long road map aimed at reconciling Thais.