Definitely all ISPs in Malaysia prohibit online casinos because the government regulates it, it's just that not all casino platforms have been blacklisted (especially new casinos) so you can still access. Reference sources regarding your country's online casino rules say:
Online gambling is technically illegal in Malaysia. While it’s clearly illegal to host an internet gambling operation, it’s not clear if patronizing a gambling site is illegal. The laws on the books were written decades ago and none of them specifically mention the act of placing bets online.
I live in a country where gambling is actually legal, but due to some religions that consider gambling is illegal... gambling is pretty strict in my country but it's still allowed if you play on licensed casino, that's just my story.
You can only play at physical casinos that are licensed in your country, and actually they are only for non-Muslims. Casino companies are more compliant with government regulations than religious ones, so they will continue to operate even in a Muslim-majority country as long as your government grants the license.