Dear k. Piyamaporn Wichiensri,
Khunpak Issara here ka. I sincerely apologize for this urgent matter, but I have just received a job offer for a position I simply cannot turn down, therefore, I don't want to waste your time having me come in for the interview on Monday morning. Once again, your time is much appreciated. I really hope this doesn't affect my relationship with you or jwt, as it is a great company and I would love to learn from your team one day.
Thank you for you kind understanding ka,