Two boats carrying an estimated 530 Rohingya asylum seekers left Myanmar's Rakhine state on 29 June, and have not been heard from since. The equivalent of a jumbo jet full of people has vanished.

It is very likely that they both capsized. The monsoon has started, the seas are rough, and the boats - usually old fishing trawlers converted to carry as many people as possible - are barely sea-worthy with unreliable engines.
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She says they would have been heading for the southern coast of Myanmar, where they would unload their human cargo.

From there they would be transported by road, via rough transit camps in the forest, through Thailand to the Malaysian border.
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An estimated 600,000 Rohingyas remain in Rakhine State, one quarter confined to miserable internally displaced people (IDP) camps, the rest surviving in precarious communities which have been caught in between the warring sides.

The military junta has been subjecting them to forced conscription. The Arakan Army, which draws its support from the ethnic Rakhine population, distrusts Rohingyas and is accused of serious human rights violations against them.

https://www.bbc.co.uk/news/articles/cr59n096mrmo