I am currently under consideration 30days for yearly marriage extension 

due to report back on 29th December. Given the current situation in the UK and the likely hood of UK quarantine on the cards, I am considering going back to the UK before the 30days and ditching the extension. Am I legally allowed to leave considering my actual extension expired on the 29th November, Worried immigration at suvarnabhum might hit me with an overstay or invent some new ruling. 
Advice needed

Thanks

Check with immigration before leaving and the might be able to contact the division headquarters approving it early.

You would not be on overstay if you left the country with a under consideration stamp.

Not sure how important it is for you to travel to the UK is but you might want to consider waiting since you will have to start all over again with a new non- visa to apply for another extension

Thanks Joe,