Update 2022-01-19: Current FCDO information from Wednesday (19 January) indicates that travellers must have a PCR test carried out when entering Malaysia. This applies regardless of whether a test has already been carried out at the place of departure. (The latter must still be presented.)
Update 2022-01-17: Full Movement Control Order (FMCO; “Total Lockdown”) restrictions are in effect throughout the country until further notice, according to information released by the Foreign Foreign Office on Monday (17 January). Meanwhile, it was also announced that fully vaccinated travellers that have recovered from COVID-19 are exempt from quarantine.