Using the existing textbox plugin will cause zooming issues..., so it is currently not possible without quite some work.
Alternatively, you might want to consider implementing your own keyboard for your mobile typing game. And there's no need to reinvent the wheel; check out the CAPX example in the link below for a working example:
https://www.scirra.com/forum/viewtopic.php?f=147&t=106727
Integrate the above example with this template, and you should be good to go.
Hope that helps!