Don Mueang International Airport (DMK)

Bangkok's newly-opened overflow airport
Word to the wise: If you're catching a taxi to the airport, double confirm which hub you're heading to. Don Mueang is north of the city, while Suvarnabhumi is east.
Talk of the town: Skytrain airport links are due to open in 2016.

Bangkok's first international airport opened nearly a century ago, but Don Mueang closed for much-needed renovations when the new Suvarnabhumi Airport opened its doors in 2006. Reopened in 2012, Don Mueang now receives several international and domestic carriers to help ease congestion at Suvarnabhumi.
Nok Air, Thai AirAsia and One-Two-GO by Orient Thai Airlines are currently based at Don Mueang, so if you need to connect with a different airline, keep this in mind—there's a free shuttle bus between the two international airports, but it can take more than one hour to make the 45 km journey.

To get to and from town from Don Mueang, a taxi is your best option—the 24 km journey takes 30-90 minutes, and shouldn't cost more than THB 400 (including all 'fees'). If you're not laden with luggage, bus 29 will get you there (eventually) for THB 20. You can also catch a train to Chinatown from the nearby Don Muang Railway Station (THB 5), but the super-busy line only runs hourly.