As is so often the case, the definitions are useful:
NFHS 4-8-1 - "A bonus free throw is the second free throw awarded for a common foul"
NFHS 4-19-2 - "A common foul is a personal foul which is neither flagrant nor intentional nor committed against a player trying or tapping for a field goal nor a part of a double, simultaneous or multiple foul."
An intentional foul is not a common foul, and it has it's own penalty. That penalty does not in any way include bonus free throws.