In a joint statement, joined by the International Organization for Migration (IOM), they called on the three countries to stop trying to push boats away from their territorial waters.
Authorities should "provide for effective, predictable disembarkation to a place of safety with adequate and humane reception conditions" and establish screening procedures to identify those in need of international protection as refugees, they added.
A migrant boat pushed back out to sea by southeast Asian nations over the weekend has not been heard from for two days, raising concerns about the fate of 300 people on board, rights groups said on Monday.