Burmese lured the minorities of Shan, Kachin and Chin to sign a Panglong Agreement to join a union that every partyv is independent and may quit the union freely:彬龙协议图片_百度百科Those are Kachin and Shan states, in North East. But thanks to the British, Burmans got Rakhine state in Nortwest too.
It's similar to the terms of India to annex their Northeastern states.