Police have now arrested 46 suspects and seized a large amount of assets in their investigation of the macau888 online gambling network, the Cyber Crime Investigation Bureau spokesman said on Wednesday.
Three people were arrested in the initial raids.
Pol Col Kissana Phatthanacharoen said another 43 of the 55 suspects subsequently wanted on court warrants had now also been arrested.
All the suspects faced charges of illegally organising gambling and laundering money.
Illegal gambling carried a prison term of up to two years and/or fine up to 2,000 baht, and money laundering up to 10 years and/or fine of 200,000 baht, Pol Col Kissana said.
The 12 suspects still at large were in hiding, in and outside the country. One was Chaiwat Kachornboonthaworn, alias Benz Demon, who reportedly postponed his planned surrender from Wednesday to Thursday, the spokesman said.
According to Pol Col Kissana, a TV actress identified suspects behind the macau888 gambling website on Jan 13 and police started their investigation on Jan 15. She is an ex-girlfriend of Mr Chaiwat.
Detectives found that macau888 was one of six online gambling websites operated by the same group of people and had about 5.5 billion baht in bets in circulation during the short investigation period.
Police raided about 40 locations from last Friday to Monday and impounded a large number of assets, including houses, condominiums and cars, Pol Col Kissana said.
Some of the impounded assets allegedly belonged to Mr Chaiwat. The 37-year-old suspect has three younger brothers. The youngest is Pol Capt Kunakorn Kachornboonthaworn, a deputy immigration inspector who took unauthorised leave in mid-January.
Police earlier said Mr Chaiwat and his brothers flew to Hong Kong in mid-January.
When the youngest brother returned, he was disciplined with seven days detention at Suvarnabhumi airport police station. He was released at midnight on Tuesday.
Police said the youngest brother denied any knowledge of any online gambling operation.