I'm no expert, but this is how I understand things stand at the moment:
Python brongersmai (Blood python) :
Found in southern Thailand and Malaysia as well as Eastern Sumatra (Indonesia) and adjacent off-shore islands such as Bangka. Genetically, this species is markedly different from the other two species (which are closely related)
Python curtus (Sumatran short-tail python, Black blood python etc etc):
Found in Western Sumatra. Separated geographically from Python brongersmai by a high mountain range that runs through the middle of Sumatra from north to south.
These are usually very dark or almost black as adults BUT - and this is new to me - there is apparently a 'dwarf' race with orange heads (that otherwise seem to resemble Borneo short-tails in colour) that are believed to originate from North West Sumatra. (Everyone still with me?) According to the Barkers, these orange-heads don't get much larger than 3 feet/1 meter in length. See www.vpi.com
Python breitensteini (Borneo short-tail python, Borneo blood python etc.)
Found on the island of Borneo, of which the northern part belongs to Malaysia and is called Sarawak, (plus independant Brunei) and the southern part belongs to Indonesia and is called Kalimantan. Sarawak and Kalimantan also appear to be separated by a mountain range, so Sarawak borneos may have the potential to be a different form than 'typical' Kalimantan Borneos. I have seen a picture of an animal from Sarawak (photographed in the wild) that was very dark, almost melanistic.
Hope this makes sense!
Phew! All that calls for a beer 
Mark