Foreign visitors arriving or departing Thailand are required to fill out an arrival/departure card. This is a two-part form that needs to be completed regardless of whether you are arriving/departing Thailand by air, boat or overland. This form should be filled out before you hand over your passport to a Thai immigration officer.
To ease the immigration entry process now you can fill out the Immigration Form(s) (TM.6) in the comfort of your home or office via Mobile Application before your traveling in/out Thailand.