In-app payment is supported by supported device except Gear & Galaxy Watch.

Yes, in-app purchases made with Samsung Pay are just as secure as in-store purchases made with Samsung Pay.

Yes, in accordance with the credit limit/ balance restrictions imposed by the card issuers. However, ALL HongLeong Bank and RHB Mastercard are not supported at the moment. 
* NOT supported card:- 
- HongLeong Bank Mastercard Credit 
- HongLeong Bank Mastercard Debit 
- RHB Mastercard Credit 
- RHB Mastercard Debit

Yes, as of version 2.8.92, you are able to make in-app purchases with Samsung Pay in the supported merchant apps.

In-app purchases occur as a payment option after you have shopped for and selected the items that are in your merchant app cart and you're ready to checkout. At this point, you can opt to use Samsung Pay, if supported by the merchant app.
1. At checkout, tap the Samsung Pay button for payment. 
2. Select the payment card you wish to use and verify your billing/ shipping address. You may wish to change your addresses, if necessary.
3. Authorise the payment with a fingerprint/ Iris image or by entering your Samsung Pay PIN.

It depends on your card issuer's policies. Please check with your card issuer.

Yes. In-app purchases made with Samsung Pay are entitle for Samsung Rewards.

Currently only Qoo10 and Samsung Billing can be used for in-app purchase.

You can contact Customer Support at 1800-22-8899 for more information.