It's not the correct image URL, try to Get the image URL as shown below

And the relative path should look like
~sitecollection/SiteAssets/Qassas.png
The image tag should look like (based on the Site Asset location)
<img src='../../SiteAssets/Qassas.png'/>
Or
<img src="/SiteAssets/Qassas.png">
[Update]
Based on my conversation with OP in chat, he tried to use HTML tag in a calculated column in SharePoint online. Unfortunately, it's blocked in 13/06/2017.
Some users have added HTML markup or script elements to calculated
fields. This is an undocumented use of the feature, and we will begin
blocking execution of custom markup in calculated fields in SharePoint
Online from June 13, 2017 onwards. We are also providing this as a
configurable option for on-premises in SharePoint Server 2016 and
SharePoint Server 2013 via the June 2017 and subsequent Public
Updates.
you can check the details at Handling HTML markup in SharePoint calculated fields
Another thread discuss this topic with some alternatives at June 13th 2017 Microsoft blocked handling HTML markup in SharePoint calculated fields - how to get the same functionality back