Auto-discovery only finds the first channel on each camera. The thermal stream is very likely a second channel, with a different RTSP url.
If you know the RTSP url for the thermal stream, you can use it to manually add to your hub ... Specify camera type "Stream URL" and enter the RTSP url.
If you don't know the RTSP url for the thermal stream, ask the support for your camera brand or on their forum if they have one. You may also be able to guess how to change the channel number by looking at the RTSP url for the first stream. To see the RTSP for the first stream, click on the camera settings (wrench icon, in the Camect UI) for the camera player that is showing the optical stream, and then click on the "i" next to "Camera Name" to get info about the stream including its RTSP url. If you see a channel number in the url, you can try changing it to 2 instead of 1 to add the thermal stream.
When trying to guess the stream, you may find it faster to use VLC to try to test the stream. Once you get one that works, you put the same RTSP url into your Camect hub.