Amornrat Kateuy was apprehended along with German national Hans Peter Walter Mack, 56, who was allegedly a customer at a house in Tambon Nong Prue, Bang Lamung district.
Police, who were staking out the house after receiving an allegation of prostitution involving underage girls, said they spotted Amornrat riding a motorcycle with a teenage girl. The German man followed them to the house on another motorcycle.
Police said they saw Amornrat and a girl inside the house, and a shirtless German later emerged from a bedroom. When the occupants of the house refused to open the door, police broke in and found a 15-year-old girl in the bedroom, wearing only a towel.
The girl told police that the man had bought a sexual service from her and that Amornrat had taken her there to perform the service.
Amornrat and Mack face charges of human trafficking and procuring/buying a sex service provided by an underage girl.