Query the post which have a thumbnail

I’ve got a highlight section on the header of my website which shows the title and the thumbnail of the last X posts having a thumbnail.

Is there any custom query which allows me to retrieve only the last X post having a thumbnail?

At the moment I’m retrieving the last X * 10 posts (because not all the posts have a thumbnail) hoping that in this result I’ll have X posts having a thumbnail. After doing my query I add a condition: if (has_post_thumbnail()).

This solution is really uncertain and ugly, a custom query with a thumbnail parameter would be great but I couldn’t find any hint about it.