Usually an A320, occasionally an A321. Overall, there is a good probability (about 70%, looking at last month's data) that it will be a reconfigured A320 with flat beds.

If you fly to PEK ex-BUD on Tue/Fri/Sat, the 16h layover in DOH will entitle you to an STPC (usually the Oryx Rotana for J-class pax).