If you are arriving in Thailand via an international flight it is usual practice for flight attendants to hand out the arrival/departure cards prior to landing. If for any reason you didn’t receive one of the forms (e.g you were asleep) just ask one of the flight attendants. If there are no forms available you will need to wait until you get to the immigration area at any of Thailand’s international airports where there are tables with a supply of the arrival cards. Similarly, if you are arriving in Thailand via a land or sea crossing there will be an area close to the Thai immigration counter where the forms are kept. Pens may be available, but don’t bank on it. You’ll help yourself (and the immigration officials) if you bring your own pen and make sure the form is correctly completed before you start to queue up.