i am english, wife thai. we live in england and have done for three years. my wife has a residents visa, with no restriction. we have a duaghter she was born in england and has an english passport, how long can she stay in thailand for wish my wife. they want to go out to thailand about three weeks befor i do and then we will stay for three weeks, that is 7 weeks in total  advise please ???

I would do the easy thing and get tourist visas for your wife and child.  Not that expensive and simple.

Believe, if wife still has proof of Thai citizenship, she would be allowed visa free entry for a year but don't know requirements.  She may also have a Thai passport that she could use.  But as it seems child has not yet been registered as Thai and a Thai passport obtained it is probably easier for everyone just to stick to UK passports with visa for them.  You can just arrive and get the normal 30 day entry.

Last summer my son who was aged 10 at the time stay with his mother and family for 87 days on a 30 day tourist visa. When we went to extend his visa we were told at immigrations that there was no need because he was under 14. When we left the country after 87 days they waive the over stay and let us proceed without any problem. I have done this for the past 3 summers and have yet to have a problem with an overstay with him. He is a US citizen but I don't know if that makes any difference

The age prescribed is up to 7 years ...yours was a thing down to an individual kindness