It is not impossible, although it seems the domain of - perhaps shall we say - less profit focused airlines. In recent memory there have been an (admittedly small) number of airlines that have added a small number of 777's to their fleet, the ones that come to mind are GA and PR but there are probably others. But most, particularly of QF's size or smaller seem to avoid adding too many types, with the exception of TG - who not exactly a beacon of profitability- who seem to want to collect one or two of just about everything that is flying (A300, 320, 330, 340, 380, 737, 747, 777, 787 and 350 on order)
An interesting and relevant data point - from the beginning of 2013 Boeing increased the production of B777s to 8.333 a month (so 100 a year).
Or in 18 months Boeing have produced more B777s (and sold them) than Airbus has A380s now into it's 8th year of 139 deliveries.
The airlines taking delivery in 2014 (66 planes from 1.1.14 to 31.8.14) are shown with the link below:
The Boeing Company
They range from Aeroflot to Emirates, AA, Air China, Cathay Pacific, Qatar and as you mentioned Thai and that dreaded competitor Biman Bangladesh Airlines for example.