cannot get rid of .thumbdata3 file

Hi
I use a Samsung On7 device, running on Android 6.0.1. The problem is that I have only 8GB of internal storage and 800 MB of it is occupied by immortal .thumbdata3_1967290299 file (device storage->DCIM->.thumbnails folder)

What all unsuccessful steps have I taken:
1. Deleted it (yeah, a 1000 times!)
2. Replaced it with dummy files of same name.
3. Tried making it read only but no explorer app could do it saying it is not allowed in some devices.
4. Removed all files from my phone/SD Card which require a thumbnail view.

Absolutely futile.

After a day or less it comes back. And even when it looks like deleted, the space is still occupied. The "Smart" manager app shows 1GB in 'other' files, and when I explore it, total device memory used (select all folders -> properties), it shows just 146MB.

As a result, my device memory is always full, forcing me to uninstalling almost all important apps since they could not be moved to SD Card.

Somebody please help.

Thanks a lot.
Piyush.