@Rochelle ******
1. Are you using Chiang Mai immigration?
2. You will need the forms (at the immigration office), and
A. Your passport and:
a. a copy of your data ("picture") page
b. a copy of your most recent visa (if you have one)
c. a copy of your most recent stamp
d. a copy of your departure card
B. 2x passport pictures
C. 1,900 THB.