It inhabits primary and logged evergreen rainforest, almost exclusively in the lowlands, rarely ascending foothills to 1,500 m but typically below 600 m. Small flocks visit fruiting trees (usually figs Ficus spp.) and are generally encountered high in the canopy. It is largely sedentary, although populations may fluctuate in response to fruiting cycles, and nocturnal movements have been noted.

Treron capellei occurs from peninsular Thailand and Peninsular Malaysia to Borneo (including Brunei, Sabah and Sarawak, Malaysia, and Kalimantan, Indonesia), and the Indonesian island of Sumatra (BirdLife International 2001). It was once widely distributed and at least locally very common, but serious declines have taken place, such that it is now highly local and scarce. There are no recent records from Java (eBird 2022). In the early twentieth century, flocks of 200–300 birds were reported as normal in Peninsular Malaysia (BirdLife International 2001). Regular flocks of 20-30 birds in Taman Negara, and reports that it remains locally common in Belum Temenggor, suggest that sizable populations may still persist within large forest blocks in Malaysia (Yeap Chin Aik in litt. 2007, Iqbal et al. 2012). The species was absent from several recent surveys in Kalimantan (eg. Meier 2005, Brickle et al. 2010, Sheldon et al. 2010), or recorded in small numbers (Slik and Balen 2006, Wielstra and Pieterse 2009, Wielstra et al. 2011, Woxvold and Noske 2011, Wielstra et al. 2012). However, 48 birds were reported roosting on the edge of secondary forest in East Kalimantan in November 2011 and up to 25 were seen at a logging concession in Melawi district, west Kalimantan in March 2011 (Iqbal et al. 2012). At least 50 birds were observed inside the Danum Valley conservation area, Sabah in May 2009 (Iqbal et al. 2012). Little is known about its status on Sumatra, where most lowland forest has now been totally cleared, but reports of flocks of 40+ in Way Kambas National Park in May 2006 (Iqbal and Iqbal 2012) and of 15 on the Kenpar Peninsula in July 2020 (eBird 2022) indicates populations persist here too, but perhaps only in large forest blocks.

Conservation Actions Underway
It has been recorded in several protected areas, including Taman Negara (Malaysia), Gunung Palung and Tanjung Puting National Parks (Kalimantan), Gunung Leuser and Bukit Barisan Selatan National Parks (Sumatra), and Gunung Mulu (Sarawak).

Conservation Actions Proposed
Conduct comprehensive surveys to establish its current distribution and status, and gather data on its movements and ecological requirements. Formulate a management strategy for Sundaic birds largely reliant on lowland forest.
Promote effective management of existing protected areas in the Sundaic region and the expansion of the protected area network. Lobby for reduced logging of lowland forests throughout its range. Establish High Conservation Forest (HCVF) within plantation areas at remaining forest in Sumatra and Kalimantan as buffer zone for its movements.