Police and rescue workers were called to the scene, a hotel on Nanai Rd, at about 4am.
The woman was found conscious on the floor in an area behind the building with two broken legs and other injuries.
Rescue workers from the Kusoldharm Foundation administered immediate first aid and rushed her to Patong Hospital.
Patong Police identified the woman by name. She is reportedly a Belarus national.
The woman had returned from Bangla Rd but discovered she had forgotten her room key, police said.
In an attempt to gain access, she climbed the building’s fire escape to reach her second-floor room. However, due to her intoxicated state, she lost her footing and fell, police reported.
Police are continuing their investigation to confirm no foul play was involved.