Security forces in Myanmar have killed at least 739 people since a February 1 military coup ousted civilian leader Aung San Suu Kyi, according to a local monitoring group.

The Myanmar military has stepped up the use of lethal force as it seeks to quell mass protests against the junta, with an estimated 250,000 people now displaced, according to UN envoy Tom Andrews.

Leaders and foreign ministers from the 10-country Association of Southeast Asian Nations are set to hold talks on the mounting Myanmar crisis in Jakarta on Saturday.

Coup leader Min Aung Hlaing will travel to Indonesia for the summit, in his first overseas trip since the putsch, Nikkei Asia reported.

His involvement has angered activists, human rights groups and a shadow government of ousted Myanmar lawmakers.

Indonesian president Joko Widodo and Thai prime minister Prayut Chan-O-Cha discussed the summit in a phone call on Thursday morning.

During the conversation, Prayut acknowledged that the situation in Myanmar is a challenging issue for peace and stability in the region, according to a press statement.

But Thai Foreign Ministry spokesman Tanee Sangrat confirmed Prayut will send Foreign Minister Don Pramudwinai in his place because he must stay home to deal with the coronavirus situation gripping Thailand.

ASEAN countries are aware of international expectations to deliver concrete outcomes from the talks, Tanee said.

"It is now up to ASEAN family members including Myanmar to safeguard ASEAN's unity and credibility," Tanee told an online press conference on Thursday.

There have been some calls for Myanmar to be expelled from the bloc, which generally has a hands off approach when it comes to the internal affairs of its members.

United Nations special envoy for Myanmar, Christine Schraner Burgener, is expected to leave Bangkok for Jakarta for meetings on the sidelines of the summit.

International condemnation of the coup and violence continues to build but the junta has so far largely weathered the backlash.

Overnight, the US Treasury department announced sanctions on Myanmar pearl and timber exports.

"The Burmese military derives significant funding from state-owned enterprises in the natural resources market," Office of Foreign Assets Control director Andrea Gacki said in a statement.