The 26-year-old holidaymaker - who has not been identified - was partying with her partner but returned alone to the hotel at 3am after a bust-up.
Her boyfriend walked back at around 6am and found her lifeless body in the room on the popular holiday island of Phuket before frantically trying to revive her.
Police and rescue workers arrived after being called by a couple in a neighbouring room who had rang for help.
Ruamjai Rescue Foundation
But the woman was pronounced dead at the scene and her body was taken to hospital.
Lt Somkiet Sarasit, from Chalong police station, said: ''The young woman hanged herself. There was no fighting and no cuts to her body.
''The man said that they had been out together. They had an argument and she returned early. They had been fighting about silly things.
''It was suicide and we're not looking for any suspects. The body has been sent to Wachira Phuket hospital.''
Lt Somkiet said the woman's boyfriend pleaded with them to revive her but her irises were were not responding to light and ''her skin was getting dark''.
''The British Embassy have been informed and have contacted the woman's family in the UK,'' he added.