Seven suspects have pleaded not guilty to charges in connection with the crackdown on zero-dollar tour scams in August.
They were among 13 defendants, including the six firms they ran, to enter pleas at the Criminal Court yesterday.
The six companies were OA Transport Co, Royal Gems International Co, Thai Herb Co, Bangkok Handicraft Centre Co, Royal Paradise Co and Baan Kanom Thongthip Co.
The suspects are: Somkiat Khongcharoen, 57, managing director of Fuan Travel Co; Thawal Jaemchokechai, 59, an executive of Fuan Travel; and Winit Chantharamanee, 69, a manager of the same firm.
The others are from the same family, and are: Nisa Rojrungrangsi, 61, managing director of Royal Gems International Co, Thai Herb Co, Bangkok Handicraft Centre Co and Royal Paradise Co; her husband Thongchai, 60; their son Wasurat, 26, managing director of OA Transport; and their daughter Saithip, 35, director of Baan Kanom Thongthip.
All are charged with operating tour guide services without charging fees, damaging tourism, taking advantage of tourists, operating unauthorised tour guide services and laundering money.
Prosecutors forwarded the case to court on Oct 25 after authorities on Aug 27 raided companies allegedly involved in the country's biggest zero-dollar tour network.
They were accused of operating illegal, poor-quality package tours and related businesses catering mostly to Chinese visitors.
Zero-dollar tours offer cheap package deals in which tourists are pressured to buy overpriced goods and services.
The investigation was later widened to two other companies: Fuan Travel, a travel agency, and Baan Kanom Thongthip Co that sold souvenirs.
According to prosecutors, the defendants committed the crimes between March 24 and Aug 31.
Fuan Travel catered to Chinese tourists in Thailand while 2,500 tour buses from OA Transport were used to serve them. Both firms provided their services free of charge.
OA Transport allegedly had tour guides take the tourists to stores, selling overpriced goods, operated by its affiliated companies.
All defendants entered not guilty pleas. The court set the start of their trial for Jan 30.
Meanwhile, the crackdown on zero-dollar tours is not expected to hurt Thailand's appeal among Chinese tourists.
Earlier this week, Siam Commercial Bank's Economic Intelligence Centre said Thailand still had high potential to draw more Chinese tourists despite the impact of the recent crackdown.
According to the centre, Chinese tourists to Thailand represent 9% of the 100 million Chinese people making overseas trips annually and they make up about 30% of total tourist arrivals in Thailand.