There are lots of ways to say Terima Kasih a lot in malay :
1. Terima kasih banyak = thanks a lot
2. Terima kasih sangat-sangat = thank you very much
3. Terima kasih sayang = thanks love
4. Terima kasih sebab tolong = thanks for the help
And you can reply with "sama-sama" which directly translated as "together'
But it actually means, "terima kasih juga" which means 'thanks to you too'.
In Malaysia we say thank you a lot of time, sometimes for no apparent reason.
You can also reply them with :
1. "Sama-sama"
2. "Eh tak apa" = Eh dont mind
3. "Tak ada masalah" = no problem
Hope this helps :D