you need to apply online for the Non-Immigrant O visa from your home country. The Thai Embassy in your home country will then , after approval, send you the E-visa after which you can travel to Thailand and start the process to get your marriage visa.
You absolutely cannot get the Non-Immigrant O visa from Khon Kaen immigration after arrival !!!
nope !! I just went through the process from Non-Immigration O to marriage visa and you definitely don’t need to do get your passport translated 🤣. Maybe if your passport is in Russian or Chinese, but not when it’s in English