When you take a CMB card to Singapore, it is not called a deposit. It is called an international remittance. The handling fee is charged by the bank in Singapore. And you need to make sure that the CMB card in your hand can accept international remittances, and What currencies can be accepted for deposit?

If the bank card you are talking about is a debit card only, then you will need to see the UnionPay logo when using it. Even if it has VISA or MASTER on it, there are these when you go abroad. It cannot be used on machines with the mark.

Overseas countries should have restrictions on the amount of foreign currency cash that can be carried when leaving customs. You can ask for advice, that is, you can open an account locally first, and you can Bring as much as you want and exchange it into RMB when you get back. This saves on handling fees.