Chalong Police confirmed that the missing tourist, named as Yuan Wenyi, from Hubei, was last seen swimming at the southern end of the beach at around 2:50pm.
His girlfriend, 27-year-old Wu Haoming, from Henan, told police they entered the water together at about 2:30pm, but after she returned to shore 20 minutes later, she noticed Yuan was no longer visible in the surf.
Ms Wu raised the alarm at around 3pm. Rawai Municipality officials, lifeguards and rescue teams began searching the area at 3:15pm but were unable to locate the tourist.
The search was called off at 8pm due to worsening weather and rough seas, with strong waves and red warning flags in place at the time of the incident. Officials confirmed no CCTV cameras in the immediate area captured the event.
Pol Col Rungrit Rattanaphakdee, Superintendent of Chalong Police, said officers are coordinating with lifeguards and rescue units, and that the search is scheduled to resume at 10am today (Oct 2).
Police noted that the victim and his girlfriend were the only swimmers in the red- flagged area at the time.
Further investigations are continuing.