Capt Thanom Thongpan of the Tha Chatchai Police was called to the scene, a rented room in Soi Makhamkhu, Mai Khao, at 1:45am.
Officers arrived with rescue workers to find the girl, Sutharat Jamsang, hanged by a rope tied to a clothes rack rail.
She was still dressed in her Girl Scout’s uniform.
Capt Thanom said police believed the girl died not more than three hours before her body was found.
Police found no signs of a struggle or forced entry into the room, Capt Thanom added.
“The girl lived with her mother, who went out at 6pm last night (Aug 16) to get some fish for dinner. When the mother came back, she found her daughter,” Capt Thanom said.
The mother, Suthisa Suthaprot, 42, told police that she and her daughter never argued, Capt Thanom noted in his report.
“Sutharat was a student at Hongyok Bamrung School in Thalang. She had been awarded a certificate of commendation for her performance in school activities,” he added.
Ms Suithisa suspects her daughter might have been heartbroken as Sutharat had been downhearted since she came home unusually late – at about 9pm instead of her usual 7pm – last Saturday night.
Messages marking a conversation between Sutharat and her boyfriend were found on Sutharat’s phone, Capt Thanom said.
“Regardless, we have yet to close the case as we are continuing our investigation,” he added.
If you or anyone you know is in emotional distress, please contact the Samaritans of Thailand at their 24-hour hotline 02-713-6791 (English), 02713-6793 (Thai) or Thai Mental Health Hotline at 1323 (Thai).