All the boats appear to have been abandoned as Thailand, their usual destination, cracks down on the trafficking of ethnic Rohingya Muslims bound for neighbouring countries, after the discovery of dozens of remains in mass graves at "slave camps" in the Thai south.
More than 1,000 migrants from Bangladesh and Myanmar landed in Malaysia after being dumped by human traffickers in shallow waters off the resort island of Langkawi, police said.
"We think there were three boats that ferried 1,018 migrants," said Langkawi deputy police chief Jamil Ahmed, adding that the number was expected to grow as more migrants are picked up around the island.
In the early hours of Monday, Indonesian search and rescue teams discovered another boat drifting off east Aceh with 400 men, women and children from Myanmar and Bangladesh aboard, Aceh provincial search and rescue chief Budiawan told AFP.