Robertas Murza on the Yahoo's Canon S1iS list reports:
The .thm file is a thummbnail picture shown when you view the files in the camera. Actually it is a jpeg file -- first frame of the movie.
I checked this out by renaming MVI_0092.thm as MVI_0092.jpg. Sure enough: PaintShop Pro displayed the picture (see image above). It's a 160x120 JPG image that even include EXIF data.
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