If your friend has turned off the Read receipts on Whatsapp and you would like to know whether he/she is reading your messages or not just follow below steps.
How to Know Whether your Whatsapp Message Have Read
Open your Whatsapp and send a Whatsapp audio, if they open the audio the grey tick will turn into blue even when the Read receipts is Unticked.
If it is in Blue color ticked then it means you are just ignored.
Another Whatsapp Trick
Want to See Someones Whatsapp story without knowing them
Just go to Whatsapp Settings->Privacy and Untick the read receipts.
Check this link to know How to Check Deleted Whatsapp Message