By default, the Seek Thermal app will apply a watermark of the Seek logo on the corner of any thermal images you take. There are also options to include the date/time of your image as well as your location. All three of these watermarks can be enabled or disabled by visiting the Image Preferences section within the app settings.
Just tap the "gear” button in the lower right corner to reveal settings, and then go to Image Preferences > Image & Video > Watermarks.