Well, obviously Ukraine has got their own war now, so the military trade relationship they had with the Myanmar junta must be well and truly over. I hope.
But the others seem like likely candidates.
I just took a look and it seems like some of the biggest Foreign Direct Investment in Myanmar in the past couple of years has been Singapore and China; other direct investors are Japan, South Korea, Bangladesh, India, Hong Kong, Taiwan, the UK, the US, Switzerland, Belize, Seychelles, Samoa... (sources include Reuters last year, the junta this year. But there was a huge funding drop this year according to The Irrawaddy).