When Tang ran out of sanitary pads while serving time in a Thai jail, the 42-year-old convict bled right through her uniform and all over the white, tiled floor.
Lunch was ruined. Tang felt humiliated.
That morning, she had expressly asked staff for extra pads, sensing the shame to come, but was told to wait on the say-so of a supervisor.
“The officer made an angry face. She asked me why I didn’t purchase any backups, and that the prison didn’t have enough pads," said Tang, who spoke on the condition of anonymity for fear of retribution.
“I felt so ashamed that I cried."
Many inmates in Thailand suffer the same monthly indignity as Tang, jailed last year for embezzlement, and are never sure what sanitary products they will get - if any - or when.
Last year, Tang said each female inmate at Chaiyaphum Prison, which houses some 2,100 prisoners about five hours north of the capital, got 12 sanitary pads, 10 times less than the 120 inmates are due under an annual quota.
Thai law requires all prisons to provide sanitary pads to female inmates free of charge, but does not specify how many.
Some prisons lack budget and can run short, said Saovakon Jeadsadaruk, an expert in penology at the Department of Corrections, the department that oversees Thailand’s 143 jails.
“We admit that there is a shortage of pads at some prisons, since we are allocated only 50-60% of the total budget that we requested to purchase personal items for female inmates," she told the Thomson Reuters Foundation.
With women making up 14% of the prison population, Thailand has one of the world’s highest ratio of female inmates.
Most serve two to five years for drug-related crimes.
The number of women incarcerated for violating state or local laws has risen sharply since 2008, when Thailand had 26,321 inmates against more than 44,000 now.
Of those, about 40,000 need sanitary pads. Tampons are sold in Thailand but are rarely used for cultural reasons.
Nathee Chitsawang, an advisor to the Thailand Institute of Justice, a research organisation, urged prisons to act quickly to ensure they had enough pads to avoid discord among inmates.
“When there is a shortage, there is a possibility that problems might occur, such as stealing or being berated by prison officials for asking for more pads," he said.
Saovakon said her department has received no reports of inmates stealing pads, but promised she would investigate.
Penal Reform International, an international organisation promoting fairness in the criminal justice system, said prisoners with periods deserved better treatment and supplies.
“Denying access to basic hygiene necessities like sanitary pads in places of detention is a violation of women’s right to dignity and bodily integrity," said Triona Lenihan, policy and international advocacy manager at the NGO.
“Body searches can be especially humiliating for women that are menstruating, and long transfers without bathroom breaks also pose a particular risk. Women should not have to suffer in this way."
The Corrections Department says it tries to fill the shortfall with donations from individuals and NGOs, and that inmates can buy pads from prison commissaries with money they are given by visitors or have earned from prison labour.
But four former female inmates interviewed by the Thomson Reuters Foundation estimate that more than half of all inmates receive no family visits so lack the cash to top up.
Many prison stores also have little in the way of stock and sell what pads they get at prices above the market rate.
Tang said she relied on a gift of less than 1,000 baht ($33) whenever her mother visited her, then frequently borrowed extra from a fellow inmate, who charged 20% interest.
Women’s rights groups want the government to keep its word on pads and provide ready and reliable supplies.
“All inmates should be provided with free access to pads without any conditions," said Chumaporn Taengkliang, co-founder of Women for Freedom and Democracy, a pressure group.
“Once they have adequate access, there will be no need to buy or steal."
In September, Tang left Chaiyaphum Prison on royal pardon.
She said the prison had not handed out pads all year and she worried about the impact on her fellow inmates.
“The prison should provide pads to those who request them without having to go through any problems like I did," she said.
“Sanitary pads are the most important item for inmates who don’t have money."