A THAI woman married a Hong Kong merchant and was brought here to work as a prostitute with the promise that she would get $20 per client, the District Court has been told. Prosecutor Michael Delaney said Ouddong Saowalak had calculated that in the 14 months until her alleged pimps were arrested, she had received $200,000 from prostitution. But Saowalak refused to testify against her husband, Chan Kwok-ping, yesterday. On trial before Judge Caird are merchants Chan Hor-nam, 59, Yuen Hong-mei, 37, and Chan Kwok-ping, 32. Both the Chans face a charge of bringing Saowalak here for prostitution. Chan Hor-nam and Yuen are also alleged to have lived on her earnings. Her husband faces a charge of aiding and abetting the other defendants. Mr Delaney said that in about May 1991, Saowalak was working in Bangkok when, through a Thai woman known as ''Aree'', she was introduced to Chan Kwok-ping. The Crown alleges that to enter and remain in Hong Kong and work as a prostitute, she married him on June 12, 1991, in Lamphun province, Thailand. ''Aree'' and Saowalak arrived on November 9, 1991, and were taken to the Wong Koon Villa in Portland Street, Kowloon, and introduced to Chan Hor-nam whom Saowalak understood to be her employer. Mr Delaney said she lived there until the arrest of all the defendants on the night of February 12 this year at the villa. He said Yuen arranged for her to serve customers in various locations. Clients paid more than $200 a time for sex with her. She agreed with Chan Hor-nam that she would serve 1,000 customers, receiving $20 per customer, with the remainder of the money going to him and Yuen. After the first 1,000 customers, she would be able to retain $75 per customer, the court heard. The hearing continues.