Hello my stamp expires on Feb 20 and I can extend 1 month more how can I do it how much time and money will it take please

Guideance please

Thank you

I am kiwi 69 years with weathered 800K in BKK BNK in own name. On Non Imm "O" -Retiement. + a current extension (expires March 27 2021) and 90 day onlne report (done 2nd Feb 2021). My current lease (Chuttachuk) expires 31st March and have now signed new lease for Nonthaburi. I have copies of the new landlords Thai ID, plus Tabien Baan data pages. New lease starts on March 1st when I will relocate. Landlady does no seem to accept her obligation to report so will self-register change of address when I shift. Processing-wise am I best to complete this before dong my new extyension? Or can they be done together?