Passenger Service Charges
All airports charge a fee for each passenger that uses their facilities. Most airports in most countries have arrangements with the airlines to build these fees into the ticket price. However, some countries in Southeast Asia still collect the taxes independently, at the airport. The fees are always collected from departing passengers only, hence the term "departure tax". How and where the tax is paid varies from airport to airport. In some cases, the tax is paid when checking in, while others may have a separate counter to pay the fee after checking in.
The amount of the fee is usually different for domestic and international passengers, and these may vary from airport to airport in the same country. Note that the fees are almost always payable in the local currency only. If you try to pay in another currency, it may be accepted, but at a very unfavorable exchange rate.
Check the main page for each airport as well as the "Departures" page for information on the exact amount of the Passenger Service Charge for any particular airport.