RM300 for Petrol, you can consider UOB One Card where you earn 5% for Petrol BUT for most other transactions you only earn 0.3% cash back.

I agree with you OCBC Titanium MasterCard will be good for you, so if you annual income is RM36K/year, go apply for it. If you don't apply for it, 100% won't be approved.

Now, since you got Maybank Petronas, you can easily get the FREE For Life Maybankard 2 Cards. If you are in Klang Valley, just drop by Maybankard Centre at 1U, KLCC or MBB HQ. You can then use the Maybankard 2 AMEX to pay your Telco, TNB & TM bills and shopping at Giant and Jusco to earn 5X Treats Points everyday PLUS 5% cash back on weekends which is better than your MBB Petronas. I think this option is good, when you need to pump at Petronas, use your existing Petronas card.

Really no point in getting the UOB One Card if you pump at Petronas because your existing Petronas card already earns your minimum 5X TP or 2.5% cash back (or 4% with 8X TP on Saturday and Sunday) when you redeem for cash voucher. So effectively you only earning maximum 2.5% extra and for RM300 Petrol, that is extra RM7.50/month or RM90 per year and less RM50 GST, you only earning RM40 per year, wasting time.
Bro,

Option 1 - get a Supp Card from Australia? But of course the conversion fee is high, so not a very good option.

Option 2 - next time you come back, go to your bank in Malaysia and see if you can apply for a credit card. Maybe can email them and ask too.

Option 3 - you can get a local credit card if you open a Premier/Priority/Privielge Banking Accounts in Malaysia and then supp the cards to your parents.

Option 4 -  ask your parents to go a open joint Citibank Savings Account (better still if you back and also joint with them) where BOTH can be issued Citibank Debit Card on the spot from a single account. You in the meantime go open a Citibank Account in Melbourne (at Collins Street because the China Town branch can do nothing). You can then sent money instantly, up to USD12.5K/day, to your parents Citibank Account when the need arise. If you had opened joint account with them like I mentioned earlier, then you can view the Malaysia Account online too from your online Citibank Australia Account and vice-versa. Click here to read my article Melbourne Victoria Australia where I did a comparison between withdrawing cash with Citibank Debit Card and Citibank Global Fund Transfer.

Option 5, ask them go get Debit Card from their existing bank and you go deposit money into their account via TT.