This English expression means "no". You use it when:

1. Someone offers to help you or give you something
2. You don't want it
3. You think the offer is strange, annoying, or unbelievable
4. You want to show that you didn't like the offer, but still speak politely

You can use "Thanks but no thanks" in situations like these:

• A friend offers you some food that looks disgusting.
• A salesman tries to sell you something that you definitely don't want.
• You got laid off last year, and now your old boss calls to try to get you to come back to your old job.