Actually , it must be for the approval letter from ministry of education(or something - i don't know , because it had been done before i headed off to Savannakhet ..
hey ,i got it in savannakhet 1.5 month ago . Wp3 and police clearance(from your country) are not required - only thai police clearance . Here you can find the detailed list. I have applied through an agency - i am not quite sure about all the details.