EDI-LHR-DEL-HKG-BJS//HKG-BKK-HKG-JFK-LIM-EZE-SCL-USH-SCL-JFK-MAD-TLV-LHR-EDI

Should be ok I think, 41000miles. You could go to ATH instead of TLV ofcourse. You can throw in a couple of segments in NA if you want to maximize miles (although you will have to pay taxes and fuel), for example throw in JFK-SFO-DFW-JFK, but I have little knowledge about NA and maximizing miles there.

You will have to buy BKK-SGN-PNH-BKK separately, PNH-BKK is flown by AirAsia. How to get to SGN, I don't know, try Vietnam Airlines (their homepage is under reconstruction).