The vital yet unglamorous task of keeping the front line ships supplied fell to the depot ships and the "China Fleet". These offer a good example of the way in which the RAN improvised the necessities of fighting a naval war at long distances from home ports. Apart from a couple, such as Platypus, all were merchant ships requisitioned or chartered for war service.
Depot Ships
The China Fleet
HMA Ships Platypus, Kuttabul, Koopa, Mombah, Matafele, Woomera, Wongala, Baralaba
Kuttabul was a 447-ton depot ship which was torpedoed and sunk by a Japanese midget submarine in their first attack on Sydney Harbour (1st June 1942). Mombah was another depot ship and collier. She was old, and immobile at times during the war; she had to be towed to Port Moresby where she became part of the naval depot. Koopa was a 416 ton coal-burning pleasure cruiser requisitioned in August 1942. She was the flotilla tender for Fairmile motor launches based in New Guinea and Mios Woendi in 1944. 
Platypus was a provisioning and depot ship; she was in Darwin Harbour at the time of the Japanese raid of 19th February 1942, tender to a number of auxilliary fighting vessels. She also ran stores into New Guinea waters.
Matafele, Woomera, Wongala and Baralaba were all requisitioned stores-carriers. Matafele (335 tons) had been doing so under the Merchant flag for almost a year when she was requisitioned for Naval Service in August 1943. A mysterious fate awaited her - she left Townsville on 16th June 1944 bound for Milne Bay, and was never seen again. A hurricane system was in the area at the time, and was possibly responsible. Wongala (402 tons) was originally Norwegian built, bought early in 1939 by the Australian government as an Antarctic Exploration vessel. She carried stores up and down the eastern seaboard, acted as guardship at Port Adelaide in South Australia, and was paid off in July 1944. Baralaba (998 tons) had been built in Germany in 1921. She was requisitioned in May 1942 and returned to her owners in February 1943.
SS Ping Wo, Yunnan, Whang Pu, Po Yang, Changte, Taiping
These were all originally ships belonging to Chinese corporations or the Chinese government. The best description of these ships is "chartered" - most frequently, apparently, by the British Admiralty. They were chartered for the vital business of moving thousands of tons of supplies without which the fighting ships could not have fought.
They did not become strictly RAN ships, or "HMAS". The designation for many of them was "VSIS" (Victualling Stores Issuing Ship) or "ASIS" (Ammunition Stores Issuing Ship). Yunnan sailed for a time "under the red duster", the flag of Britain's Merchant Navy. Their crews were by no means always or entirely RAN. Ping Wo had a crew of two Royal Navy officers, RAN ratings and sixteen Chinese seamen; Yunnan's Chinese crew jumped ship in Brisbane when they discovered their ship was about to enter a war zone. Changte and Taiping had crews of 14 officers and 106 chinese ratings in civillian service; many of these were dispensed with in war service, and some replaced by RAN personnel.
They were quite definitely not warships. Changte and Taiping had luxury accomodation for passengers, and one ex-crew-member described Ping Wo as "a rusting old heap of crap". The only armament they carried was light and defensive; obsolete 12-pounders, 40mm Bofors guns and/or a couple of 20mm Oerlikon guns.
All this notwithstanding, they had as varied a career as any warship might have wished. Ping Wo, for example, left Singapore ahead of the Japanese early in 1942 with the V&W Destroyer Vendetta in tow, and saw her safely as far as Melbourne - a two-month voyage. Eventually she became a tender to the LSIs Westralia and Manoora during beach-landing training. Whang Pu also left Singapore just ahead of the Japanese, becoming eventually a submarine depot ship, then a supply and mobile repair ship before witnessing the surrender ceremony at Morotai on 9th September 1945. Po Yang carried ammunition for US Task Force 77.7 during the Leyte Gulf operations - and was given a wide berth by all friendly ships, just in case.