They are both correct but have different meanings. It's no good (doing something) .. is an idiom that means there is no point or use in doing it; you are wasting your time doing it. For example: It's no good asking him for help. He's too busy with his own work.
Similar examples from Google:
It's no good asking – no one knows what it is and where it comes from.
It's no good asking them anything, they couldn't care less!
It's no good asking me. I haven't got a clue.
It's no good asking – no one knows what it is and where it comes from.
It's no good asking them anything, they couldn't care less!
It's no good asking me. I haven't got a clue.
On the other hand, It's not good (doing something) .. means that it's not a good idea to do it. For example: It's not good asking him for help; he will think you are incompetent.
More Google examples:
It's not good asking that, here on the internet, because there are many people, who will try take you down.
It's not good asking to move deadlines because, as a freelancer, you lose credibility.
It's not good asking strangers health related problems, better consult the professionals.
It's not good asking that, here on the internet, because there are many people, who will try take you down.
It's not good asking to move deadlines because, as a freelancer, you lose credibility.
It's not good asking strangers health related problems, better consult the professionals.
