Hey @Lorène P.   Shauna here from Support! 

There’s no way to do this at present - CSAT ratings will send once they meet the criteria. This would be a feature request - I will flag this with the Product team for you

Please provide any feedback or share any context you may have in regards to your use case here! 

Thanks Shauna! 

When CSAT is sent before the last message sent by the agent is seen by the customer, the customer sees the CSAT first, because it’s the most recent message of the conversation thread. And they answer negatively, because they think the agent didn’t reply to their question, when in fact, they just haven’t seen it.

I hope this helps!