It could be a big problem for people who go around doing their daily business with hard cash as there is the cap of 25k RM. The only upside for such people is that it becomes much easier to transact big sums of money after depositing it in a bank and then sending it through the online payment method.
And how many are they? IIRC the 25k RM is for a single transaction[1]. I'm not sure most Malaysian needs to transact at least $6k usd for a single transaction each day.
Its quite easy for the government to monitor ALL of the transactions happening online with the use of a unified payment system model which is undoubtedly being developed for this purpose.
That's true, but my point is how will they monitor the physical transactions. Are they going to install webcam everywhere? Or wiretap all their people's phone? It's easy to say you must not transact more than $100 in cash each day, but monitoring millions of people is not easy peasy.
[1]
https://www.channelnewsasia.com/news/asia/malaysia-to-impose-cash-transaction-limit-of-rm25-000-in-2020-12072710