There must be some anecdotal evidence for when elephants were re-entered Bali (after extinction) and what sources for imports were used.
The elephants at the Bali Safari Park should be Sumatran.
Link:
Elephants | Animals | Bali Safari Park
I have lately taken a closer look at elephants in Indonesian zoos and have found that the vast majority, if not probably all are Indonesian islands in origins (and without exception ... all Sumatran).
It has been reported elsewhere there is now not only a registry, but a ZIMS/Species360 record of Sumatran elephants in Indonesian zoos. A studbook is under development listing all elephants in Indonesian zoos managed by PKBSI/Taman Safari organisation with Ministry of Forestry/Environment that should include also the Elephant Training Center and Conservation Units in the field holding Sumatran elephants.
Some of the biggest field conservation holdings are Way Kambas and Seblat. Smaller ones exist at a.o. Tangkahan and Margahayu. The Way Kambas facility (Pusat Latihan Gajah - PLG) has probably been the biggest supplier of captive Sumatran elephants within Indonesia. The original plan was to capture problem elephants and relocate them to the training centers and numbers sharply increased when the forestry policy was introduced.
The idea was to provide elephants for domestication and use in patrolling and tourism riding industry. Way Kambas actually imported 2 Thai bull elephants (Tong Bai and Sengtong) - khoonkie elephants with mahout - to start the training process. These 2 bulls - allthough unplanned - did breed with the local Sumatran elephant females captured from the wilds and there is a portion in captivity that is actually hybrid Thai/Indomalayan and Sumatran elephants in the camps. There was also a preference for males for the training process ... and Way Kambas PLG does now hold a skewed group heavily in favour of males.
However, as is sometimes the case no one really had taken account of the why's and wherefore's and management, husbandry and accommodation where not well run from the outset. A number of elephants passed away and in later years issues with nutrition or frequent relocations to logging companies and others has led to some unfortunate deaths within the captured elephant group.
The realisation that husbandry and management required more training and capacity a policy of redistribution of elephants to other facilities, including zoos and commercial safari parks and tourism sites was introduced. At the same time, a registry was created to track all elephants in captivity in Indonesia, this is a Forestry Service departmental task and is reviewed every 2 years (elephant pregnancies are 22 months in duration ..., something along those lines). The goal now is also to breed elephants in conservation ex situ management.
From this source, Taman Safari organisation has more or less created the ground stock for their current captive-breeding programme for Sumatran elephants, all 3 facilities - Bogor, Pasuruan/Prigen and Bali - have sizeable herds (think big along lines of 20+ and at TSI - Bogor it is a lot more .... than that). Various zoos including Batu Secret, Lembang, Ragunan-Jakarta, Surabaya, Bandung and Yogyakarta received some of their elephants from Way Kambas.
ATM, the training centers with the largest herds close to protected areas or within them are Way Kambas and Seblat. I think there are 3 other important ones in Tangkahan, Way Bungur and Tesso Nilo. The facility that stands out is the private Barumun Nagari Wildlife Sanctuary which is led by local Batak people concerned with the welfare of what they see as their elephants!
There is one major resource for elephants in captivity in Dan Koehl's Elephant.SE, unfortunately thee task being gargantuan ... it is far from complete and in particular the various transfers of the 320+ elephants is phenomenal. Often only some individuals are known ... I would appreciate the help of some of our Indonesian Zoochat fans to fix this.