Five foreigners were arrested for visa offences during raids in Bangkok, Chiang Mai and Surat Thani from Dec 26-Jan 8.
They were apprehended by officers from the police centre to suppress transnational criminals and illegal immigrants and immigration police.
The five men -- Olawale Raimi, 33, of Nigeria; Jonas Silva, 39, of Guinea-Bissau; Riches Ogboona Onu, 44, of Nigeria; Tshepo Zuma, 37, of South Africa; Ouattara Ben Ibrahim, 21, of Ivory Coast -- were taken to a media briefing on Wednesday.
Pol Lt Gen Surachate Hakparn, commissioner of the Immigration Bureau, said they committed two forms of visa offences. Some were found have more than one passport, with different names and nationalities. Some had overstayed their visas.
Back-checking showed they had not entered or left the country as was indicated by the visa stamps found in their passports, he said.
Their visas had been revoked and the investigation was being extended to determine the origin of the visa stamps, Pol Lt Gen Surachate said.