I saw that but it also says: You can buy up to 35kgs per transaction up to a total of 100kgs.
So I should be fine there.
No, I'm actually coming from DOH - considering talking RJ from DOH > AMM > BKK as they offer luggage on piece concept and with OW plat I can get 92kgs by flying economy.
Luggage Policy - Royal Jordanian
Not sure what the extra piece charge would be but there are usually two rates with any airline - the lower rate being flying 100% with that airline and the higher rate being for multiple airlines in the journey.
If you are flying RJ DOH/xAMM/BKK you're probably better off having a totally different pnr ex BKK (or HKG) to SYD on QF as having the RJ flights (or any other airlines) in the same pnr as the QF flight, even if on two separate tickets, will generally prevent you from purchasing your QF excess luggage at the discounted pre-paid rate as the system will tell you your journey is ineligible for pre-paid luggage and you must pay at the airport.....at the much higher rate.
As you are OWE it's possible RJ may allow up to 32 kg per bag on the piece system (like AA in the USA) for the DOH/xAMM/BKK ticket although I don't know for sure. Then when checking in for QF it's multiple pieces up to the total baggage allowance. Make sure you take a print out of your baggage receipt.
Just to throw something else into the mix, if RJ permit through checkin on separate tickets they may well be able to add the QF BKK/SYD flight in as oncarriage at DOH and tag your bags all the way to SYD.
A couple of potential hurdles are the maximum amount of hours in BKK in transit for baggage to be through checked eg it may be only if your transit in BKK is under 12 hours. The 24 hour rule pretty much just dictates being able to transit at a city without it counting as a stopover for ticketing purposes.
The other potential hiccup could be that the RJ checkin system may want to charge excess when the QF flight is added as oncarriage and the RJ checkin staff at DOH may not know how to (or have the authority to) waive this despite the fact that RJ is the the most significant carrier so the piece system should apply for the whole journey.
If RJ won't through check you could then purchase the extra allowance direct with QF but check when the cut off is for pre-purchasing at the lower rate as you don't want to burn your bridges and not be able to do either.