A coalition of more than a hundred NGOs has called for an immediate international arms embargo on Myanmar, as a response to the military coup that took place in early February. Since then thousands of people have taken part in demonstrations and acts of civil disobedience, and have faced violence from the country's security forces. The military government has threatened the use of lethal force against demonstrators, at least two people have been killed after police used live ammunition.
The letter calls for the United Nations Security Council "to immediately impose a comprehensive arms embargo on Myanmar", which should ban "the direct and indirect supply, sale, or transfer of all weapons, munitions, and other military-related equipment, including dual-use goods such as vehicles and communications and surveillance equipment, as well as the provision of training, intelligence, and other military assistance". The arms embargo is necessary because any sale "could provide the means to further repress the people of Myanmar in violation of international humanitarian and human rights law." You can read the full letter here: https://www.hrw.org/news/2021/02/24/joint-call-global-arms-embargo-myanmar
A UN report published in 2019 identified companies from China, Russia, Ukraine, Korea, India, the Philippines and Israel as having done significant arms deals with Myanmar's military, the Tatmadaw.