Bangkok MRT BTS Skytrain Airport Link Map and Route Guide. Metropolitan Rapid Transit or MRT is a mass rapid transit system serving the Bangkok Metropolitan Region in Thailand. The Bangkok Mass Transit System, commonly known as the BTS or the Skytrain is an elevated rapid transit system in Bangkok.The Airport Rail Link (ARL) is an express and commuter rail in Bangkok. The line provides an airport rail link from Suvarnabhumi Airport, via Makkasan Station, to Phaya Thai station in central Bangkok.