Clearly, your English language skills are of some disadvantage to you, and I would urge you, no matter where you are employed, to pursue some courses that may strengthen your English skills, since this will be an essential skill for any senior manager in the years ahead as Thailand becomes integrated into the AEC.
Please write to me to let me know of your decision, and if it is positive, I will write a more formal job offer letter. We would be very pleased to have you on our team and hope that you may rapidly become a valuable member of our organisation.