SaiThumbs is a Windows Shell extension that will allow image thumbnails for the .sai/.sai2 files produced from SYSTEMAX's PaintTool Sai.

Featuring art by @vintagefoods_​(vf.media)!

Between SaiThumbs installations and updates you ​may​ still see cached thumbnails for .sai/.sai2 files in explorer even after uninstalling or updating to a new SaiThumbs.dll. You can clear your thumbnail cache by running "Disk Cleanup" and selecting "Thumbnails" before cleaning.