Police said that the taxi driver, Kajornsak Rungruang, 25, had admitted to attempting “to have sex” with the 23-year-old tourist after he saw her walking along the road near the Patong Library on Haad Patong Rd.
Police said he stopped his cab, got out and tried to grab her.
She screamed for help, and her cries were heard by two staff of The Nap hotel and tourist Takahiro Maruyama, who raced to intervene.
Grappling with Kajornsak, Mr Maruyama was punched in the face, resulting in a cut above his eyebrow that required 15 stitches.
Kajornsak was subdued, arrested and charged with assault causing injury.