The striker made the comments earlier this week, amid speculation that Nottingham Forest, Blackpool and Coventry City all wish to sign him.
Boyd has rediscovered his best form at Rugby Park this season - he has scored nine goals in his last 10 matches - and his manager believes that has been fuelled by the striker's ambition to prove himself at a higher level.
"I'm sure there will be loads of clubs looking at Kris Boyd, the way he has played," said Johnston, whose side play Dundee United tomorrow. "He has still got the ambition to play at the highest level. You want that. If players play with hunger, they play better. So I'm not disappointed teams are showing an interest."