Hello, I transfered my tourist visa to a non B at immigration in Bkk. last week (March 24th) and was given 90 days (based on employment and work permit). Immigration told me that I need to go to my provincial office to apply for 1 year. My 90 days is up on June 24th. so my question is, can I go to the provincial office anytime before June 24th. or does this have to be done immediately?

You do not extend a visa anyplace other than Immigration. But any time you change a visa you must re validate your work permit so expect that is what you were told to do - and that needs to be done immediately I suspect.