If I am not mistaken, it should be possible for one payment card to have two separate chips, namely one chip for Visa transactions, and the other chip for processing quick payments in local transportation.
This is the former version of DBS Visa Debit Card, issued by DBS bank in Singapore.
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There is a NETS logo on the back end of the card. In other words, once the NETS stored value of DBS Visa Debit Card is reloaded, you can use the card in MRT and buses in Singapore, as if DBS Visa Debit Card is a NETS FlashPay card.
For sure, you can swipe the card at the credit card terminal, for the payment to be processed via Visa payment network.
Nowadays, the current version of DBS Visa Debit Card no longer has NETS function.
My point is that is the card cost is not an issue, it should be possible to embed another chip in Touch n Go Visa Prepaid Card, so that that additional chip allows the card to function as a normal Touch n' Go Card. Still, I do not think that Touch n Go Visa Prepaid Card will have the additional Touch n Go chip, due to cost.