Why don't you get a hotel room? Emirates can do that for you free of charge if your in DXB for 8 hours and less than 24 hours, that's if you took the earliest flight after you land in DXB to BKK.

If not, I really don't think you can cuz I've asked about this before through Emirates and they said no.

But you can try one thing, go to http://www.emirates.com/english/dest...tSchedule.aspx
enter your flight details (only the GLA-DXB Sector), and after that click on flight services (on the flight which your taking)

after that you could find a note at the bottom that Business and First Class passengers can take advantage of the lounge if connecting to another flight. (you could print that and show it to them since that is for the 1st sector only)