Hi Akshay,
Template grid editable option looks like non editable, from that check box editable option got inherited
A templategrid is always non editable if I'm not mistaken. So you're probably better off with adding some css or javascript to show a checkbox (selected or not) based on selection.
Sjors is 100% correct. We implemented this for a data grid, adding a class to it and then have an embedded java script in the page that replaces the formatting of a selected row (shaded background) by inserting a checked / non checked checkbox (alteratively radio button for a single select) .
It’s a pity but unfortunately not possible otherwise.