Here are some other ways to say thank you in French, depending on the context:
* Merci beaucoup - Thank you very much
* Merci bien - Thank you very much (slightly more formal than "merci beaucoup")
* Merci infiniment - Thank you very much (even more formal than "merci bien")
* Je vous remercie - Thank you (formal, used when addressing someone older or in a position of authority)
* Je te remercie - Thank you (informal, used when addressing someone younger or someone you know well)
* Merci de votre/ta gentillesse - Thank you for your kindness
* Merci de votre/ton aide - Thank you for your help
You can also express gratitude with phrases like:
* C'est très gentil de votre part. - That's very kind of you.
* Je vous suis reconnaissant. - I am grateful to you. (formal)
* Je te suis reconnaissant. - I am grateful to you. (informal)