A judge has denied bail to a prominent filmmaker detained for criticising the military despite warnings that he could die in custody as he struggles to recover from an operation to treat his liver cancer.

Min Htin Ko Ko Gyi briefly fainted during yesterday’s hearing and at one point removed his shirt to show the judge scars from an operation he had three months ago, according to the Rangoon Documentary Twitter account.

Min Htin Ko Ko Gyi is the founder of the Human Dignity Film Institute and is known for his documentaries on human rights issues.

Hundreds of filmmakers and other professionals from around the world signed a letter on Tuesday calling for his immediate release.

“We are gravely concerned for his health and fear for his life,” said the letter, published by the International Documentary Film Festival Amsterdam and the International Film Festival Rotterdam.

“Half of his liver was removed and he is also suffering from heart and kidney diseases. It is very difficult for him,” defence lawyer Robert San Aung told reporters after the hearing.

He added that the defence has considered appealing for bail to the high court but that “we are afraid it would prolong the trial”.

The military’s decision to sue his client under two different laws for the same alleged offence was “unlawful”, he added.

The filmmaker has been hit with defamation charges under section 66d of the penal code and also charged under section 505a, which bans statements that might induce military officers to “disregard or fail” in their duties.

Each carries a maximum sentence of two years in prison. The latter is a non-bailable offence but the defence has argued that the judge could use his discretion in cases of poor health.

The next hearing will be held on May 9.

Major General Tun Tun Nyi, vice chairman of the Tatmadaw’s True News Information Unit, said he was unable to comment on the defence’s objection to opening two cases.

“I assume they sued him under two sections because he violated both,” he told Myanmar Now.

Min Htin Ko Ko Gyi published a series of Facebook posts in February and March denouncing the military’s role in politics and describing former dictator Than Shwe as a “thief”.

He remained defiant after yesterday’s hearing, declaring sarcastically: “I now regret saying I disrespect them… Now I will say I respect them, respect them with deep admiration!”

His detention comes amid a surge of arrests of peaceful critics of Myanmar’s authorities. Five members of the Peacock Generation Thangyat troupe were detained earlier this week after they criticised the military during a performance over Thingyan.

Human Rights Watch today called on the NLD to repeal repressive laws used to silence peaceful dissent.

“During military rule, Aung San Suu Kyi and many current lawmakers fought for free expression, yet now the NLD majority in parliament has taken almost no steps to repeal or amend abusive laws still being used to jail critics,” said Brad Adams, the group’s Asia director.

Earlier this month the military opened a second lawsuit against a Mandalay-based monk named Thawbita, whose situation is similar to Min Htin Ko Ko Gyi’s.

Thawbita was hit with a 66d charge seven months ago after criticising the military on Facebook. Then earlier this month the military opened a new lawsuit against him, which his lawyer fears will lead to a charge under section 505a.

“The army is really after me," he told Myanmar Now, "but I don’t care because the consequences are to be expected.”