Originally Posted by
HpW1981
If you really want proper undisturbed sleep during your 8hr layover, in your situation you will need to book a room at the transit hotel.
hiahotel.com
BKK-LHR return with all 4 sectors on the A380 requires an 8 hour layover in HIA on the way out, and without the hotel would be a complete non-starter for me. You also get access to the gym and swimming pool, which is a nice way to break up a long journey.