The agency has collated witness reports from Rohingya Muslims -- a minority which endures persecution in Myanmar -- who say they were forced to leave the country by groups of men armed with knives and guns.
Yasmine, a 13-year-old girl, told HRW that a dozen men came to her home in Rakhine State, home to many Rohingya, and told her she needed to leave Myanmar, which is also known as Burma, to join her brother in Malaysia.
"They dragged me to the boat, they had sticks and threatened to beat me," she said. "I screamed, I cried loudly. My parents were weeping, but they couldn't do anything. I went onto the boat with three men. When I got to the big boat... I cannot explain my feeling, I was so scared."
Another, 16-year old Arefa, said that six Rakhine Buddhists from Bangladesh, armed with knives and guns, forced her to get on a boat.
"They told me I was leaving Myanmar," she said. After a six-hour journey to a larger vessel she spent two months at sea with 95 other migrants, amid dwindling food supplies and abysmal sanitary conditions, before arriving in Malaysia.
"I don't know what I'll do in Malaysia, I have no money. I miss Myanmar, but I know I cannot go back," she said.
According to the International Organization for Migration (IOM), an estimated 25,000 Southeast Asian migrants took to the seas in the first three months of 2015.
Whether seeking a new life voluntarily or forcibly removed from their homes, migrants and refugees from Southeast Asian countries like Myanmar and Bangladesh have no choice but to put their lives into the hands of unscrupulous brokers and traffickers.
After weeks or even months at sea, they are either dumped in unfamiliar countries like Thailand, with no money, to fend for themselves, or are herded into camps in the jungles of Thailand and Malaysia where they are held captive and further mistreated.
"Survivors describe how they flee persecution in Burma only to fall into the hands of traffickers and extortionists, in many cases witnessing deaths and suffering abuse and hunger," said Brad Adams, Asia director at Human Rights Watch in a statement.
"Interviews with officials and others make clear that these brutal networks, with the complicity of government officials in Burma, Bangladesh, Thailand, and Malaysia, profit from the desperation and misery of some of the world's most persecuted and neglected people."
Yangon: Anti-Muslim marches
Nationalists and Buddhist activists in Myanmar were given permission to march in the country's largest city, Yangon, in protest against foreign pressure to provide aid to Rohingya Muslims. Burmese nationalists claim that the Rohingya minority are Bangladeshi, despite many Rohingya having roots in the country going back generations.
Nationalist religious activist Ko Min Min, told the Myanmar Times
: "I will never accept these boat people in Myanmar. I will always oppose this because they are from Bangladesh."
Phil Robertson, deputy director of Human Rights Watch's Asia division, told CNN that the government is complicit, through their sanctioning of the march.
"The Burma government hasn't done anything to rein in incitement to violence and hate speech," he said. "Allowing this kind of march to go forward... (shows the) arbitrary nature how these permissions are granted."
Thailand is due to host an international meeting on the issue of seaborne migrants in Bangkok on Friday, where the crisis will top the agenda.
Deputy Prime Minister and Foreign Minister Tanasak Patimapragorn said Tuesday that the meeting would focus on the immediate problem of helping those migrants still stranded at sea, but also address the wider issues causing seaborne migration in the region, and solutions to crack down on the human traffickers who facilitate the system.
The Bangkok Post reported
that Tanasak expected some workable solutions to be agreed upon at the meeting, but stressed that the international community should play a role in ending the crisis.
Robertson says that the meeting also needs to address the root cause of the Rohingya's plight.
"There needs to be a concerted push on Burma to end discriminatory policies against Rohingya," he said. "People like this are essentially caged up, prisoners in their own land. Given the limitations on their basic ability to survive and support themselves, it's unsurprising that they are lured by people smugglers. (There needs to be an) effective push to end the deprivation that leads them to make these kinds of decisions."
At a meeting last week, Indonesia and Malaysia agreed to temporarily accept thousands of migrants, as long as the international community helps to resettle them within one year.
"It's going to be very important for front-line states (such as Malaysia, Thailand and Indonesia) to provide full and unimpeded access to the UNHCR and assess whether they are eligible for refugee status," Robertson said.
"The one-year deadline is only going to happen if there are impartial assessments (of refugee status claims) by international agencies like the UNHCR."
He added that the IOM should play an important role in assessing if the migrants are victims of human trafficking.
U.S.-Thai military cooperation
The Thai Navy has said it will deploy a "floating base" to the Andaman Sea to offer assistance to seaborne migrants.
The vessel, the HTMS Ang Thong, will provide immediate assistance before Thailand "facilitates" migrants' transfer to "temporary shelters in Malaysia and Indonesia," Prime Minister Prayut Chan-ocha said. Thailand has so far declined to allow migrants to be sheltered, even temporarily, on its soil, and has suggested that those discovered on Thai soil will be treated as illegal immigrants.
The general said that he would welcome U.S. patrols in the region, but they should be under Thai chain of command. The military had previously referred a U.S. request to use Phuket International Airport as a base from which to conduct surveillance flights to the government's airport authority.
Camps, remains found
Malaysian authorities confirmed earlier this week that 139 graves and 28 abandoned camps discovered close to the Thai border were related to human trafficking.
Inspector General of Police Khalid Abu Bakar said that Malaysian police and border guards, as part of an operation, found a burial site which contained corpses which had decomposed to the level that only skin and bones remained.
Fences and sentry posts indicated that the camps held captive migrants, he said.
"Some of the camps found showed that they have been occupied since 2013, and the latest two camps were abandoned two to three weeks ago," Khalid told Bernama
, the Malaysian state news agency.
Those who have experienced the camps tell of a brutal existence as the brokers seek to extort the migrants' relatives.
"Brokers told our relatives to send the money and beat us when we were on the phone. They're very bad people," Sharuf Khan, a Rohingya migrant who spent seven months in a jungle camp, told CNN affiliate ITN. "There's little to eat here. Some people starve. Many are sick.
"One man didn't have the money to pay the ransom, so the brokers beat him. They handed him over to the camp guards, and said, 'you can finish him.' The guards took a rope and hanged him."