kaiotes your baggage allowance will be the standard allowance for rhe class of travel on the DOH-BKK sector. This is the Most significant Sector and, unless QR give you the F allowance for the entire journey, is what you are entitle to for the entire journey. The actual baggage allowance is shown on your E-ticket. Because of mixed classes QR can give you a greater baggage allowance than the IATA Resolution 302 requires but it is up to them. They are not required to do so.

This is a vague answer because you give no details of the cabin class, and indeed carrier, for the DOH-BKK sector. I am assuming cabin class J on QR.