If you have the (extra) budget, grab a book called "Kaplan Ielts" na krub. Go through the book, take plenty of exercise. If you know someone that teaches one on one tutoring on Ielts, it would also benefits you na krub. (Iam a big fan of one on one tutoring than going to lecture class/in group). 6.5 is not far, practice makes perfect and goodluck krub.