Three Mongolian nationals seen on security camera footage stealing from travellers at Suvarnabhumi airport two weeks ago were arrested when they returned to Thailand to steal again.

The trio, two men and a woman, were apprehended at the airport after arriving back in the country on Monday evening, Pol Lt Gen Surachate Hakparn, commissioner of the Immigration Bureau, told a media briefing on Thursday night.

Khishigbata Bold, 40, Turmunkh  Burengargal, 41, and Ms Ulzibayar Baterdene, 35, were detained on arrest warrants issued by the Samut Prakan provincial court on March 13 for collusion in theft.

German tourist Voker Willi Mauss, 59, filed a complaint with police at Suvarnabhumi airport police station on March 8 that his wallet went missing shortly after he arrived at the airport.  As he was about to get in a cab he realised his wallet, containing about €300, was gone.

Airport security camera footage showed three men and a woman following the German from Gate 3 on the first floor of the passenger terminal to the airport taxi area. The woman was seen pickpocketing the victim's wallet.

She and the other suspects then walked to the Airport Rail Link station, where one of them stole a wallet holding A$500 from Australian tourist Michael Stuart Williams. 

The gang later took the Airport Rail Link train to Phaya Thai station, where they changed to a BTS skytrain.

Police investigators found that the gang had also pickpocketed from passengers boarding BTS trains, said Pol Lt Gen Surachate.

The suspects were all Mongolian nationals. The gang worked systematically, dividing tasks among its members with the woman doing the pickpocketing and then passing stolen wallets and other items to other members. 

By then, the gang had left the country. However, three of them arrived back in Thailand on the evening of March 18 and were promptly arrested by police investigators and airport security staff. They were handed over to Suvarnabhumi airport police for legal action.