Usually you can do as many international transfers as you like but they need to total a minimum of 65k baht each and every month for a full 12 months prior to applying for the next extension and you also have to honour the terms of the current extension
there's no real problem with short overstay IF you make it to the airport. The problem comes if you are involved with the police while on overstay, even 1 day, when you will be arrested and deported.
no, just surprised that it should be so easy. I have a permanent home in the UK but it doesn't count as I rent it out (I don't want it to lie empty) so it's not available to me. I have pretty similar assets to you all in the UK too, continue to be a UK tax payer and yet I'm not a UK tax resident because I don't spend enough time there to be one.