Hiding your online status is really very simple but before mentioning those steps I just want to give you a quick reminder that as after you hide your online status on Facebook you will also not be able to see who among your friend list is currently online. However, before disabling you will get some option and you can select any of them as per your comfort.

So here are the following steps through which you can disable your online status: 

• At first login to your Facebook profile
• Click on the chat option from the right corner
• A list of contact will open who are currently active
• Then click or tap on the gear option

Then go to the advanced setting and you will see three option:- 

• Turn on chat with all friends except
• Turn on chat with only some friends         
• Turn off chat

"Simple ain't it"