@Georges *******
, keep in mind that a yearly extension of stay based on raising a half thai child is NOT issued on the same day like retirement extensions are :O
Extensions based on marriage to a thai and raising half thai children go under consideration for 30 days from the date you apply for it and then you go back to get the extension stamped into your passport after that.
IF you applied for an extension based on raising a child AND you were going to leave the country during that 30 days you'd have to get a re-entry permit AND you'd have to be back in the country within those 30 days so you could back and get the year stamp inked into your passport.