We would still advise users to reload your Touch ‘n Go Card and have some balance in it. The balance in the Touch ‘n Go card and the eWallet are separate and not interchangeable.
However, with PayDirect, toll fares at selected highways are deducted directly from your eWallet. Hence, you just have to ensure sufficient fund in your eWallet and do not have to worry about reloading your Touch ‘n Go card for toll payments. For list of Highways that are PayDirect-enabled, follow this link.
Below are the articles that may be useful for you :
What happens if I do not have sufficient funds in my Touch ‘n Go eWallet?
What happens if I do not have sufficient funds in both my Touch ‘n Go eWallet and Touch ‘n Go card?
Can I reload my Touch 'n Go card via the TNG eWallet?