"Terima kasih banyak."
Terjemahan:Thank you very much.
"A lot of thanks" can be heard and read, so I think it's correct.
It seems more often used in a sentence, with "to say a lot of thanks", "give you a lot of thanks", "A lot of thanks to you".
Contoh penggunaan: http://www.linguee.fr/anglais-francais/traduction/a+lot+of+thanks.html