If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Malaysia.
Food Act 1983 Food Regulations (1985) Regulation 361 (2014) and Food (Amendment) Regulations 2016 Increased from 18 to 21 in December 2017, effective October 16, 2018. There will be an 18-month grace period for sellers to comply. After the grace period, anyone caught selling to persons under 21 can be fined up to RM10,000 and jailed up to 2 years. Malaysian identity cards include a designation of religion, which allows enforcement of the religion-based sales restriction.
You can find more legal details and links here:
Wikipedia Legal Drinking Page