The bodies of Phuangsri Kroksamrang, 58, and Somjai Insamnan, 27, were found floating in the Adelaide river south of Darwin by tourist boats last Wednesday.
They are thought to have drowned after being thrown from a bridge with their hands and legs bound. Investigators have suggested that their killers may have intended them to be eaten by crocodiles to prevent the bodies being found.
Prostitutes working in the city initially blamed the deaths on organised criminals attempting a takeover of the trade, which is officially tolerated in most Australian states. Police have been cracking down for several months on Hell's Angel gangs involved in the Darwin escort business, but that line of inquiry is no longer being pursued.
Ben William McLean and Phu Ngoc Trinh, both 18, were arrested at a house near the Queensland capital of Brisbane on Wednesday night and were due to be sent to the Northern Territory today.
A white Toyota van seized at the house resembles the one in which the women were last seen alive, last Monday afternoon.
The van was spotted near a cash machine in Darwin on Monday night when money was being withdrawn from Ms Phuangsri's account, and again in a nearby town on Tuesday morning when two withdrawals were made.
Brothels are illegal in the Northern Territory, and the women operated out of a motel in Darwin's suburbs. They had been working in the city since the mid-90s, and both are believed to have separated from Australian husbands.
Ms Somjai's 10-year-old son lives with her family in the northern Thai village of Lanhin, where her monthly cheque for 10,000 baht (£140) was worth five times what her relatives were able to earn.
Police believe the women were held hostage for up to 24 hours by their killers, and had been in the river for between 18 and 30 hours before they were found.
It is thought that little would have remained of their bodies if heavy rains and flooding in recent weeks had not driven crocodiles away from the Adelaide river.
