It’s done online, for the none O there is no place on the form for insurance. I have recently done it, if you don’t have the 800,000 laying around, Anna visa in Hua Hin will do a multi entry one year extension for 28,500. That is if you have the none O, and a bank account. She is doing it for my friend.
I am also flying on Wednesday, going to do mine tomorrow afternoon. As I don’t land until 13.25 on Thursday local time. Which is where the 72 hours is counted from.