A part of me suspects that it's also a lot more troublesome to apply to perform in Malaysia. The last time I checked, the organising company in Singapore just needs to have the right entertainment license and they can easily apply for a work permit for artists. Whereas Malaysia has this 39 page beauty.
And if you're holding your concert in Sabah/Sarawak you have to submit your application twice to PUSPAL and the state government. Yeah, it's not looking good for us.