Applicants can find process of test fee refund of each test center that you registered at below links;
Bangkok Test Center
Website: https://www.ojsat.or.th/main/jlptrefund-r2-1-2563/
Facebook: https://web.facebook.com/OJSAT/posts/3252717351419265
Chiang Mai Test Center
Website: https://bit.ly/2YtrCC0
Facebook: https://web.facebook.com/ojsatn/posts/3026452517444868