@Meaux **********
. . there is no one-year Non-Imm-ED visa.
You need to start out on a 90-days single entry Non-Imm-ED visa with the documentation the language school provides you with, on the E-Visa system outside of Thailand, and once after having entered Thailand on this visa, you can apply for the one-year Extension of the Stay Permit based on Education (ED)
What you however can do, is applying for the 5-year DTV on a Muay Thai training seminar from a licensed training camp.
For this visa application, among other things, you need to prove you have a minimum of 500,000 THB or equivalent, for a minimum of three months, on a bank account in your name