12 Arrests Follow 4-Month Bookmaking Investigation : Gambling: The $20-million-a-year sports- betting ring conducted in Thai used high-tech equipment. Police say the leaders are still at large.

A dozen people have been arrested on suspicion of participating in a $20-million-a-year bookmaking ring operating out of the San Fernando and San Gabriel valleys, Los Angeles police and sheriff’s officials said Monday.

Although the sports-betting ring’s estimated annual cash intake was described as “mid-level” for Los Angeles County, Deputy Police Chief Mark A. Kroeker said its use of “a sophisticated array of high-tech equipment” such as facsimile and telephone-answering machines was “unprecedented.”

Kroeker also said that the ring’s top leaders have so far eluded arrest and that a joint investigation by police and the Los Angeles County Sheriff’s Department would continue.

“We’re not convinced we have Mr. Big here, but we are convinced we’ve made a big entry into this organization,” said Kroeker, the San Fernando Valley’s top police official. He was joined at a press conference by Sheriff’s Lt. David Kading, and Los Angeles Police Lt. Faryl Fletcher and Sgt. Bill Martin.

The arrests Sunday culminated a four-month investigation and followed the searches of nine homes. During the searches, investigators seized $7,800 in cash, answering machines, tape recorders and a long sheet of slick facsimile paper that Kroeker said showed a list of wagers, payments and debts.

The ring was harder than usual to crack because its business was conducted almost exclusively in Thai, authorities said. A Thai-speaking sheriff’s deputy worked on the investigation, and a civilian volunteer helped during Sunday’s searches and arrests, the law enforcement authorities said.

In the pyramid-like operation, clients placed their bets with low-level workers, who would, in turn, phone or fax the wagers to higher-ranking bookmakers operating out of their homes, police said. The bets would be placed on sports ranging from football to horse racing.

Police also seized at one San Fernando Valley home a small, black book listing jewelry, homes and luxury cars that Kroeker and Martin said appeared to have been purchased with the betting operation’s illegal proceeds. They said state and federal tax investigators had already been contacted because of the apparent unreported income.

All 12 people were arrested on suspicion of felony bookmaking, which carries a maximum penalty of three years in state prison and a fine of $5,000 for those with previous convictions. All 12 posted bail and were released, police said.

The San Fernando Valley-area residents arrested were:

Mayuree Natesiri, 45, of Northridge, a gas station owner; Panya Natesiri, 48, of Northridge, a gas station owner; Eck Stone, 48, of Sepulveda, an actor; Yongyuth Popiemlarp, 57, of Northridge, a shipping firm clerk; Kanchanasuda Chooyoot, 33, of Van Nuys, a restaurant entertainer, and Camol Praditpol, 53, of Eagle Rock, a restaurateur.

Those arrested in the San Gabriel Valley and elsewhere were:

Karik Leartanasan, 42, of Rowland Heights, who was listed as unemployed; David Lo, 40, of Cerritos, a sewage treatment plant worker; Doungjai Chumpraseat, 37, of Cerritos, listed as unemployed; Arunee Supkitpol, 45, of Monterey Park, a garment worker; Vison Pichedwatana, 32, of Monterey Park, a card dealer, and Chintana Bliss, 40, of Monterey Park, a garment worker.

Only Mayuree Natesiri and Praditpol could be reached Monday, and both declined to comment.