Can anyone tell me that if I take my new Thai WIFE back to england with me in March 2022 will she be able to stay for maybe 8 months instead of the statuary 6 months visiting visa, she has already been to england 4 times before but as then my Thai girlfriend.

maybe change the title so it's more useful

I think if your wife stayed longer than 6 months she would be classed as an over stayer which would adversely impact any future visa applications.  Is she not planning to settle in the UK.

Ask The UK Border Control Agency the circumstances under which she could legally stay longer

The conditions for which she could apply to extend her stay are extremely limited, https://www.gov.uk/standard-visitor/extend-your-stay

 

Those considering an application would take into account the reasons given for the trip in her original application, including her proposed length of stay, and her continuing ties to her home country.

 

I’ve taken the liberty of altering the title of your question, to give forum members a clue as to what you’re asking.