This is almost certainly the airport that you will arrive in Bangkok from any international flight.
How much does it cost to get to Bangkok with a taxi, from Suvarnabhumi International Airport (BKK)? It costs around 300 Baht to central Bangkok on a metered taxi.
Getting to Bangkok via train: There is a train line ("Suvarnabhumi Airport Rail Link Express Service"), which takes just 15 minutes (direct - no stops) and costs 150 baht each way.
This is used for domestic flights, so if you are flying from Bangkok to other Thai citie then you will probably end up here.
A taxi from Bangkok to Don Muang will cost around 300 baht.