I see, well I'm truly screwed then as my wife has just left me, leaving my daughter in my care. So I either go to Ho Chi Minh or Pnomh Penh every 3 months and pay for a new non o visa or survive for as long as I can on as many SETV I can get with extensions. Greaaaat.
Tony I'm in the same situation as you. I have a Thai wife and half daughter too. I think if you are travelling with them it will be fine. I've never had a problem. They target lone travellers who have many tourist visas. But I'm travelling alone.
I see so immigration just transfer over the entry stamp and extension stamp. I'll bring the old passport over to the airport just in case they ask questions or if they want to see the visa. Thanks for the info.