You can delete your credit/debit card details from the Linked Payment Methods page on Shopee App.
Go to the Me tab > select the ⚙ icon > Linked Payment Methods > select the relevant card > Delete > enter your password > Continue.
⚠️Note
Once you select Continue, your credit/debit card details will be immediately deleted. If you accidentally deleted the card details, add your card details again on the same page.