you get 2 land border bounces per year so you have 1 left, if you want to stay longer buy a 60 DAY SETV for 1,900THB at a Thai Consulate/Embassy [FYI if you buy this then do a land border crossing this does not count against your 2 land border crossings per year] you can extend that visa for another 30 days to get 90 total days out of it...there is no limit on Air border crossings just be advised you will run into the one over zealous immigration officer that will say otherwise then say DENIED....
with the 6 month METV it goes live the day it’s placed in your passport…so to best maximize your days in Thailand it’s best to have a flight booked ASAP after you receive it