The thieves then produce clone cards to empty bank accounts.
Thai Bankers' Association secretary-general Twatchai Yongkittikul said the fake keypads feel hard to the touch and that cardholders should immediately cancel their transaction if the keypad feels strange and notify the bank immediately.
He did not say exactly when this new technique was detected, but said thefts had occurred "occasionally".
He said the banks, "if proved at fault", would be responsible for the stolen money, adding that though financia.
In a TV interview yesterday, Twatchai said he believed it was a large-scale operation that involves computer experts and people with experience in plastic and rubber products, as the fake keypads looked very much like the real thing.
According to Twatchai, the technique also involved the use of false decoders, which record personal information of cardholders stored in the magnetic strip on ATM cards. The thieves then used two sets of information - pin numbers and cardholder's information - to produce cloned ATM cards to withdraw money.
Twatchai said he did not think bank officials were cooperating with the thieves.