Yes it is possible… not recommended, but possible. People have put them into the following places:
As shown by the blue location, some people put multiple tags into the same triangle space between the metacarpals of the thumb and index finger. As long as there is at least 5mm space between the two tags, and at least 3mm to 5mm space between tag and nearest bone, it should be ok. Of course, nothing is guaranteed, but that would be the minimum safe distance I think.
I personally have placed an xEM into the space between my pinky and ring finger metacarpal bones on the back of my right hand. It’s not the preferred location, but it’s worked out just fine.