Valuation is usually carried out by authorised firms and their representatives (usually banks and their associated valuation experts) after taking into consideration of recent property transaction prices, and other market factors. You can also ask a real estate agent or mortgage broker for an indicative value.
For details on the property valuation process in Malaysia, do refer to this: https://www.propertyguru.com.my/property-guides/how-property-valuation-works-14584
Alternatively, you could engage the services of a registered valuer for an official valuation report for a fee. This is an option: http://my-property.com.my/
We hope that you'll get the valuation you require.