Can use TNG ewallet in SG? What sim and plan is best for 3days?

I come for travel. I don't like to hold cash. Can I use tng ewallet for purchase around tourist and hawker places?

If no, are there any ewallet app for tourist? Example like "BAKONG TOURIST" in Cambodia?

What sim card is recommended for 3 night stay? Where is the less expensive place to buy after landed at airport?