The currency in Malaysia is The Malaysian Ringgit. On your Malaysia tour, it is recommended to carry a combination of both cash and card. While cards are widely accepted across the country, there could be some pockets where cash is needed. There is no limit on the foreign currency you can take into Malaysia, but do consider the ATM withdrawal charges as well.
You can also consider using a Travelcard, as it is secure considering it requires identification card before usage. Malaysians occasionally refer to Malaysian ringgits and you can exchange currency either at the airport or at authorised agencies that are spread across the country. Keep in mind that the notes are in good condition as agencies do not accept torn notes.
Check with SOTC for the best rates before your holiday.