you must apply for the metv not the single entry. If you got the single entry you get 60 days and extension is done at immigration not the airport. Single entry visa is not a multiple entry
did you apply for the TR60 single or the TR60 multiple entry. The Multiple is the one that suits. If it expires on the 8 June you could re-enter Thailand on the 6 or 7 june and get another 60 days