Thanks for all your help guys..

Does this mean if i don't do anything, I can stay for 7 days and leave the country 7th April without being charged for overstay?

The stamp reads "Extension of stay permitted up to 31st March 2022. Holder must leave the kingdom within the date specified here in. Offenders will be prosecuted' Sorry forgot the last part of the stamp says holder must leave. So are my only options to either get an new contract/non-B with my school or apply for an extension of stay?

I have a non-B visa passport date stamped 31st March. My contract is ending at my school 31st March. Unfortunately, I told the school last December I was leaving the country after the contract finishes. I was planning to leave the country 30th March and booked my flight. All was ok until the war in Ukraine and my flight got cancelled. The only other available flights are 3 times the price! I'm now trying to re-negotiate another contract with my school, stay for another year, then go back to Russia next year after the war is over, but the school have other teachers available and I'm not sure now if they'll now give me another contract. I shouldn't have told them my plan to leave last December! So are you saying I have 7 days to leave after my contract ends or I have to apply for an Extension of stay?