That doesn't apply if you get the multiple entry 'O' based on retirement I believe. It only applies on a non-immigrant 'O' multiple entry visa obtained in your own country and after obtaining the three month extension, giving you fifteen months, then you have to leave Thailand.
I heard it's two months before and three months after you get the extension. Mind you, beware the Thai taxman, I believe there after your money, retiree or not.
So I presume you are already paying some sort of tax in the USA? I don't pay any tax in the UK because I don't have enough income to be taxable, but if I moved to Thailand they'd want a lump of my pension.
Has anyone any info on the rumour that foreign retirees that are staying in Thailand on 'O', or O-A Visas have to pay income tax on their state pension from their own country? I've read conflicting information about this.
Not very well explained. Multi entry tourist visa gives you 60 days, then apply for 30 day extension = 90 days. Then border run and depending I believe which border you cross, possibly the Thai immigration take a dim view if you cross the border and return the same day. When you do get back into Thailand then you get another 60 day stamp, then apply for a 30 day extension, then another border run and same procedure for your final entry, 60 days + 30 day extension.