i'm not sure if you can edit it with Camtasia. I have no clue if Camtasia can open .avi files. Last time i tried was with its own format (recorded with Camtasia).
To edit with Camtasia, you have to change the default setting of Bandicam.1. Motion JPEG and PCM codec (Recommended for most users)
If you want to edit the recorded video with Camtasia, we recommend you use "Motion JPEG and PCM" codec. 2. H.264 and PCM codec (Recommended for advanced users)
If you can see the "H.264 (NVIDIA/INTEL/AMD)" option in Bandicam, please follows the steps below:
1) Install both x264vfw and x264vfw64 codecs from http://sourceforge.net/projects/x264vfw/files/
2) Choose the "H.264 (NVIDIA/INTEL/AMD)" encoder.
3) Choose the "PCM" audio codec.
4) Choose "1" at the Keyframe interval.