Ms Piyamas confessed to committing similar thefts three times and received US$1,000 per each occasion of smuggling.
According to an investigation, an Indian man named Kumar Ramesh leads the gang, and his close friend "Lylia" was employed as local staff at the Thai embassy.
Ms Lylia stole on average about 100 visa stamps per month from a box in the visa office. Mr Ramesh contacted gang members to find likely customers wishing to travel to Thailand, such as those from Nigeria and Cameroon or those involved with drugs or other cases and suspected by Thai authorities when crossing the border.
"There are about 2,000 visa stamps in a box. Smugglers gradually stole the stamps to avoid suspicion at about 100 stamps each time from around October last year until June this year," said Pol Col Chatchai Iamsaeng, the Immigration Bureau's commander-in-chief.
Thai police are now seeking a court order to issue arrest warrants for Ramesh, the gang leader, as well as other Thai persons involved in the visa smuggling case. Ramesh is now suspected to have fled and stayed in Malaysia.
Police said the gang started by producing counterfeit watermarks on documents and later found ways to contact local staff working at the embassy to join the gang and smuggle visa stamps.