If you dislike the idea of read receipts you can disable the option all together through the app’s settings – but this works both ways. If you don't want people to see when you've read their message, you won't be able to see when they've read yours.
Launch WhatsApp and tap the three dots icon at the top right of the screen, then choose Settings, Account, Privacy. Within this menu you’ll see the option ‘Read receipts’, which can be disabled by unchecking the box beside it. Also see: How to avoid WhatsApp viruses, scams and hoaxes.
How to read a WhatsApp message without the sender knowing: Aeroplane Mode
If you want to keep read receipts enabled, but don’t want a sender to know that you’ve read their message, there’s another trick that can temporarily prevent the two blue ticks appearing. Also see: How to install WhatsApp on a tablet.
When you receive a WhatsApp message the notification will appear on the lock screen (if you aren't using the phone) and in the pull-down notification bar. Before you open the message, enable Aeroplane or Flight mode on your phone, which will kill your Wi-Fi and mobile data connection. WhatsApp won't be able to connect to its servers to tell the sender you have read that message.
Once you have read the message exit the conversation and, in the Chats view, tap and hold on the conversation to access various options. Choose Mark as unread, then turn on your data connection.
Note, however, that we found this method gave inconsistent results across devices, and would recommend you instead turn off read receipts (as we detailed above), or look to our next tip.