"Thank you! You are very kind!"

Translation: Cảm ơn! Bạn rất tử tế!

[ADUCCK]

"tử" = death;
"tế" = health;
"tử tế" = kind...

[alfredo_555]

Why "Cảm ơn, bạn là rất tử tế" is wrong?

[okorz001]

rất replaces là. They are not used together.