Apparently Malaysia is really easy about driving licenses so you shouldn’t have a problem on an international and probably not on the Pakistani one either.
I was advised to hire a car from KL for my whole trip; to get me around KL (apparently you really don’t want to be dealing with public transport) and around the rest of the country. The distances are fairly short. From KL to the east coast, it’s a 3 hour drive. Even staying in KL for a week after spending a few days in the city itself there are lots of places nearby. Melaka is max 2hr drive south from KL.
Cameron Highlands about 2 hours drive north. You could make a day trip out of it and come back to KL. Or I’m guessing you want to spend longer, so drive to Ipoh, get a hotel there for a few days and make day trips from there in different directions.
If you want to be more adventurous, you could travel to Malaysian Borneo.