They give human traffickers a little money up front, the rest coming while they are in transit. Urgent calls are made to their families demanding $2,000 or more before they can continue on their way.
Until recently, the first stop along the route was neighboring Thailand, where they were held in secret in the jungle. Those unable to come up with ransoms risked being held for months, sometimes longer, enduring beatings and getting little food, water or medical attention. Many died; in recent weeks authorities have discovered dozens of shallow graves in abandoned camps.
The tactics of smugglers changed in November following a crackdown by Thai authorities on human trafficking networks. Instead of bringing their "passengers" to land, they held them on large boats that were effectively offshore camps. They shuttled them to the Thai-Malaysian border on smaller, rickety vessels once they were paid off.
When the heat turned up - not only traffickers but also politicians and police were getting arrested - brokers and agents got spooked. People were no longer allowed to disembark. Still more boats kept coming until there were up to 8,000 migrants stranded at sea - both Rohingya, fleeing persecution, and Bangladeshis, who fled their country largely for economic reasons.
This month, some alarmed traffickers started abandoning their ships, leaving their human cargo at sea without fuel, food and clean water. More than 3,000 people have so far washed to shores in Southeast Asia.
The United Nations estimates an equal number are stranded at sea.