Dear Khun Saowakhon,
I'm not sure the text "Dear K. Nattawut" that you mention previous email. Do you mean me?
If yes,I would like to say, Thank you email for a job interview.
I read the job description then i think, I'm not suitable for this job.
So, I decide not to proceed interview for this position.
Again, thank you for your time and consideration.
I hope our paths will cross again in the future.