I'm looking at two overnight layovers in the BKK airport going to and from Hanoi in a few weeks. I arrive around 11:00pm and leave around 7:00am both times. Any thoughts on sleeping in the airport vs. booking a Hotel near the airport? Taking a taxi to the city and staying up all night? I'm used to roughing it, but if there's nowhere to lie down in the airport, or if it's discouraged, I expect I'll be better off finding a nearby hotel.
thanks, Dan

There is an air-side hotel, I've never stayed but others have reported that it is acceptable. Suggest you make reservations.

There are two airside hotels, one in int'l term 1 and another in int'l term 2 (these terminals are essentially one big, connected terminal). They are on the 3rd floor in the passenger departing area and are operated by Louis Taverns/Miracle Grand. I've tried to get a working link, from the BKK airport site, but have not been successful.

http://www.miraclegrandhotel.com/dayroom.html

Note that there is a Louis Tavern hotel outside the airport too, this is a different and separate hotel from the air-side hotels.

If you head into town you'll have to clear immigration (twice, entering and exiting) and pay the 500 baht departure tax (once when exiting). All in all you'd have ~ 4 1/2 hours of sleeping if you chose to go into the city and get a hotel (factoring in clearing immigration, taxi, check-in, check-out, taxi, check-in at airport, clear immigration).

There are many all/late-night spots esp. for food, Ratchada comes to mind (which is not too far from the airport), which might be fun, but might be challenging to get to/from without local knowledge?

There are a lot of treads about this in the Asia forum of fodors.com. Use the search function and it should give you all the info you need.