Attorney Khin Maung Zaw is defending the ousted civilian leader, who was detained during the February 1 coup on an obscure charge under the country's import and export law for having walkie-talkies at her home.

On Wednesday the military regime hit Suu Kyi with a second criminal charge, accusing her of holding an election campaign event last year which the junta claims breached coronavirus restrictions under natural disaster management laws.

"We hope for the best but are prepared for the worst," Khin Maung Zaw told AFP by phone, adding he is hoping for a fair trial.

The veteran human rights lawyer said he applied on Wednesday for permission to speak to his client and receive instructions ahead of the next court hearing on March 1.

"When will this be granted? I don't know," he said.

Khin Maung Zaw said he has not been allowed to meet with Suu Kyi in person and is worried about the confidentiality of their discussions over video or phone calls.

"It's more appropriate to meet with her in person without being interfered by anyone," he said.

- 'Anything can happen' -

At the next hearing the judge, prosecutor and defence lawyer will discuss the complexity of case and work out a time frame for proceedings and schedule for witnesses.

Khin Maung Zaw says if the case is classed as simple it could be wrapped up in six months, but if deemed more complex it could drag out for a year or more.

"In this country anything can happen," when asked if there was a danger of long delays.

At Tuesday's hearing Khin Maung Zaw's junior colleague was barred from being inside the room with the judge and prosecutor who could see Suu Kyi by video link.

"He couldn't see her because we weren't allowed to participate in the video conference because we aren't duly appointed at the time," he said, adding his colleague could hear the voices of the judge and defendant.

A United Nations special envoy has hit out at the "secretive trial" of Suu Kyi and President Win Myint, who also faces the same charge under natural disaster management laws.

The pair are in a "safer place" and "in good health", according to military spokesman Zaw Min Tun who addressed the media in Naypyidaw Tuesday.

"It's not like they were arrested -- they are staying at their houses," the general, who became the country's vice-minister of information after the coup.

The United States and Britain condemned the new charge against Suu Kyi, and renewed demands for her release.

More than 450 people have been arrested since the coup, according to the Assistance Association for Political Prisoners monitoring group.