@Jerome *******
you would have to get a re-entry permit to leave on the 90 day Non-O visa AND you'd have to be back before that 90 days ran out so you could apply for the year extension too
The financial requirements to get the initial 90 day Non-O visa are 400K baht in a thai bank account in your name when you apply for the visa itself
The financial requirements to get the year extension are 400K baht in a thai bank account in your name only for 2 months before you apply for the year extension