BA's flight leaves LHR at 21.35, so it could be them
On their website they currently quote £684 but that's to BKK so you would need to pay for another flight down to Phuket, with Nok Air etc so which adds around another £60, which means £744 to beat.
EVA Air 02/Nov 21.30 >> 15/Nov 13.10 (note daytime return flight) quotes £679 plus the £60 flight BKK/HKT = £739.
Singapore Airlines 02/Nov 22.15 >> 15/Nov 12.40 (note daytime return flight) quotes £555.80 You then need a flight to HKT which Silk Air price at £170 SIN/HKT = £725.80 but it would mean flying back to SIN on 14th and staying overnight. There might be a low cost carrier that flies back early enough for the 12.40 departture from SIN.
Not sure how you feel about going via Middle East...
this site
Benz Travel Cheap Flights on-line I have used before and had no problems. They quote for flights 02/Nov to 15/Nov, LHR to BKK...
Kuwait Airways (no alcohol !!) via Kuwait £391.40
Qatar Airways via Doha £406.60
Etihad Airways via Abu Dhabi £409.60
Emirates via Dubai £372.60
in each case you should then add £60 for the BKK/HKT flights.
Hope some of this helps
