The Rufous-collared Kingfisher ranges across Southeast Asian lowland and low-montane forests in countries like Malaysia, Indonesia (Sumatra), Thailand, Myanmar, and Brunei, inhabiting shaded streams, jungle rivers, and moist forest areas, being somewhat elusive but not that rare, especially if you learned its call. It is one of the two “forest kingfishers” of West Malaysia tropical forest, the other being the Banded Kingfisher, with one of their calls having some similarity.

Males have blue wings, females have green, spotted wings. Whilst the Cap/Head of Males have a green/blue mix; those of the females have a darker, spotted green cap.
For overall color the males are generally more vibrant with blue tones on top, while females appear more greenish and speckled.

It is fairly common (but in small numbers) all over lowland to sub-montane forest of West Malaysia, including Bukit Panchur State Park, near Nibong Tebal in Seberang Perai Selatan only for Penang State. It’s world-wide population is probably declining, it do not need complete forest cover and can be found in degraded forest, but can’t be found in wooded habitat and orchards or above montane habitat.

https://datazone.birdlife.org/species/factsheet/rufous-collared-kingfisher-actenoides-concretus