The Thais and eight men were booked at Sadar police station for breaching the Immoral Trafficking Act.
The arrests followed public complaints.
Police raided the Crystal Mall at Banipark and arrested the manager, four Thai girls and helpers at the Thai Harmony Spa.
Six Thai girls, three customers and the manager of Crystal Spa were also arrested.
The girls charge between Rs3000 (Bt1,600) to Rs 6,000 (Bt3,200) for a massage with illicit relations, police said.
Police have the Thai girls’ visas and passports and are checking their backgrounds.