Any idea how to go about this? Thx

Getting them to do what? What age students? What qualifications do you have? Does your permission to stay in Thailand allow you to work? Unless you're already teaching or want to work for some organization that provides tutoring & that vets its teachers, simply announcing that you want private students would not attract an overwhelming number of applicants ... to pay you for some undisclosed purpose.

You are going hard on him, Suradit, although your post have some valid points. If I may say so...

I think the best way for the OP to get pupils is through a teaching job in a school. There will be a good chance, that some parents will wish him to teach their kids.

Other than this...try posting in news papers, slips on poles, etc. Get in touch with as many thais as possible, then mouth to mouth will do it.

Good luck