user103496

NETS is a debit system, not credit card. As a tourist, you don't need to care about this Again, yet another falsehood. NETS processes many credit card payments and does routinely reject foreign credit cards, as per my comment above. Wikipedia: The nationwide acceptance infrastructure is the largest in Singapore and includes 54,000 Unified Point-of-Sale (Unified POS) terminals (which accept NETS, NETS FlashPay, debit and credit cards such as VISA, Mastercard, American Express, UnionPay, RuPay and JCB) and 94,000 QR acceptance points (for payments via NETSPay, PayLah!, Pay Anyone and Mighty).

Email from one merchant: "our system currently only accepts Singapore addresses". Email from another: "NETS has rejected the transaction".

The local merchants/payment systems may also only accept local addresses, postal codes in the local format (6 digit), or phone numbers in the local format (8 digit). If your card details don't match those, then you can't use your card.

Foreignness doesn't come into it This is false. I have a foreign card and occasionally run into trouble using it in Singapore. For example, you can't top up your EZ-Link card using a foreign card (though they now say that from Dec 2024 onwards, this will be possible but with a hefty 3.5% admin fee). Foreign cards also frequently fail on online payments.

@dROOOze: the specific request itself ("sing a song in Chinese") is weird. Maybe they wanted to try to exclude OP.

It was probably just a joke (or a jokey excuse to not give the guy the freebies). Every speaker of a Chinese language agrees that "中文" includes Cantonese.