The hotel inside the airport is an extension of the Louis tavern (priority pass lounge) and stats at 2400thb for 4 hours. Basically an awful ripoff. The priority pass lounges are open 24/7 if you're inclined to lean that way but the airline lounges are all closed overnight. This assumes your onward flight is international. If domestic then you might not even gain access to the lounges.

With 10 hours and departure at 10am just get a hotel proximal to BKK with transpo and breakfast and get some sleep.