You are allowed to enter Thailand 2 times a year without a Visa and will get issued a 30 day exemption each time. Total 60 days ten with no Visa. If over 50 and you don't mind paying 1000 to 1500 usd you can hire local agent who will do all the work for you and get you approved for a 90 day OA visa which they will convert to a 1 year retirement visa. You must be 50 y.o or older. Total is 15 months. After that the agent will charge approximately 500 to 700 usd to renew your retirement visa annually. It will cost you extra if you want to leave Thailand and re-enter during your stay here on a retirement visa.