The thefts have forced the GSB to suspend indefinitely the services of about 4,000 ATMs which were manufactured by a Scottish company.
GSB director Mr Chartchai Payuhanaveechai said Tuesday that the bank had suspended the services of the Scottish-made ATMs on August 8 after officials found out that 21 of the ATMs had been hacked with the use of Malware programme.
The hackers withdrew 40,000 baht each time from six ATMs in Phuket, two each in Surat Thani, Chumporn, Prachuab Khiri Khan and Petchaburi and five in Bangkok in Sukhumvit and Vibhavadi Rangsit areas.
Mr Chartchai said the bank had notified the Bank of Thailand about the electronic thefts so that commercial banks which have in their services similar brand of ATMs be warned and taken appropriate preventive measures.
There are about 10,000 ATMs in service in Thailand, including about 4,000 of the GSB.
He said that the stolen money belong to the bank, not the customers, so GSB would demand compensation from the manufacturer of the machines.