A 22-year-old girl shot herself at Surat Shooting Range on Wednesday with a 9mm pistol and died later at hospital.
She left a letter telling the reason for her suicide at home, a Surat Thani police investigator said.
According to police, the girl, Ms Chanidapa Boonkhum, fired one shot from a rented 9 mm pistol of the privately-run shooting range and was fatally injured.
Range staff immediately rushed her to Surat hospital where she was pronounced dead on arrival.
The surveillance cameras at the range caught her arriving to practise shooting at 3.00pm.
She paid for 20 rounds of 9mm cartridges before practising shooting at the firing line. She emptied 18 rounds from the handgun, leaving two in the firing chamber.
She pointed the gun at her right temple and then pulled the trigger, police said.
Investigation later revealed that she was a resident from Trang province and she had come to the range to practise for the past three days.
She left a last letter at home in Trang with a farewell message to her family before she committed suicide, police added.