Police were first informed of the incident, at a hotel on Rat U-Thit 200 Pi Rd, at 5:37am on Saturday (Mar 8).
The Russian man, 44-year-old Aleksandr Belinskii, had been physically assaulted. He had suffered multiple injuries and was taken to Patong Hospital for treatment.
Mr Belinskii told police that he was attacked by three men who had entered the room with the intent of raping a Finnish woman. He was attacked when he intervened to protect her, he said.
Patong Police reviewed CCTV footage and tracked the three suspects to a different hotel also on Rat U-Thit 200 Pi Rd, where they were arrested.
The individuals taken into custody were named by police as Aksu Cemre Can, 30, and Aksu Ali Cem, 22, both German nationals, and Yanyana Salman, 23, a Turkish national.
According to initial police investigations, the suspects claimed they had accompanied the Finnish woman to her room after a night out.
Upon arrival at the room, they encountered her boyfriend, Mr Belinskii, and a heated argument ensued. The situation then turned violent, leading to the Russian man sustaining injuries, they said.
The three men were taken to Patong Police Station and charged for the assault, pending further legal proceedings.
Meanwhile, police continue to gather evidence, including CCTV footage and witness statements, to determine the full circumstances surrounding the incident.