I attempted this for the METV: 6month bank statements and other financial evidence - all has to be one upload, and still under 500kb.... Its impossible. As Robert says above, just send a load of illegible shite.
the point is airlines in the UK can (and do) refuse boarding if you dont have a return flight (or a return flight within the term of your entry stamp). They should call the airline for assurances that they will be allowed to travel(and get a letter to state as such, to present at check in.) There would be no issue at thai immigration.
You wont get a third 60 day stamp as the visa had expired. The re entry would have only maintained the end date of the extension - which as you were staying out 1 month from the 28th it would have also expired.