
These are species with at least one recorded territory in Malaysia, not a national checklist: a bird list from eBird or Avibase is more complete. The counts follow recording effort as much as wildlife, so a country with more visitors and more naturalists will show more of both.
The species with the most open occurrence records in Malaysia, among those a photograph exists for. Most recorded is not most numerous: it rewards animals that are common, conspicuous and live where people go.

Pycnonotus goiavier

Acridotheres javanicus

Aplonis panayensis

Hirundo javanica

Treron vernans

Oriolus chinensis

Geopelia striata

Todiramphus chloris

Orthotomus ruficeps

Collocalia affinis

Rhipidura javanica

Merops viridis
The reference database has no regions filed under Malaysia.
The field guide covers Malaysia on the map, but none of its species have an entry written for them yet.