As of March 8, 2023, the central bank reserves of Malaysia and Singapore are as follows:
Malaysia: 134.5 billion USD
Singapore: 345.2 billion USD
As you can see, Singapore has a much larger central bank reserve than Malaysia. This is due to a number of factors, including Singapore's status as a global financial hub and its strong economic growth.
Here are some of the reasons why Singapore has a larger central bank reserve than Malaysia:
Singapore is a global financial hub. Singapore is a major center for international trade, finance, and investment. This means that there is a lot of money flowing through the country, which helps to boost the central bank reserve.
Singapore has a strong economic growth. Singapore has consistently recorded strong economic growth over the past few decades. This has helped to boost the country's tax revenue, which has in turn helped to increase the central bank reserve.
In contrast, Malaysia is a less developed country with a smaller economy. This has led to lower tax revenue and a smaller central bank reserve.

Sg has recently announced that they will cap their IMF reserve a to a certain % of gdp. So they now keep most of their reserves or transfer extras to their sovereign wealth funds GIC now worth about $usd 700 billion or Temasek now worth $usd500+ billion.
They are beyond rich ok.