Two illegal immigrants from Vietnam and Cambodia died in a Thai detention centre in the early hours of Wednesday, police told dpa.
The men, a 72-year-old Vietnamese and a 55-year-old Cambodian, were found dead in a detention room by a cell mate returning from the toilet in the middle of the night, said Sastra Onrassamee, police chief of Thung Mahamek district in Bangkok.
No cause of death has been established, pending autopsy results, Sastra said, adding that the room in Bangkok's Immigration Detention Center (IDC) where the men were found was holding a total of 15 detainees at the time.
Thailand, which has not ratified the UN's 1951 Refugee Convention, does not recognize the status of refugees and asylum seekers, who are treated as illegal immigrants and incarcerated.
Many Thai immigration detention centres are "severely overcrowded, provide inadequate food, have poor ventilation and lack medical service and other basic necessities," according to Human Rights Watch.
"These immigration detention facilities have long been reported to fall far short of international standards, but the Thai government has not acted to address the serious problems," Sunai Phasuk, the rights group's senior researcher in Thailand.
Wednesday's deaths "should be a wake-up call for the Thai government to end its abusive policy of incarcerating asylum seekers," he added.
A number of illegal immigrants have died from various illnesses while in detention in recent years.
Last November, a 16-year-old Rohingya girl died from an alleged blood clotting disorder after three years in detention in southern Thailand.
In May 2017, a 36-year-old Christian Pakistani fleeing persecution in his home country died after suffering a heart attack in the IDC.
The latest deaths come amid a crackdown on illegal immigrants by Thai authorities labelled "Operation X-ray."