problem with these is they are not accepted when applying for a visa that required a local account. I've had a UOB Thai bank account for 10 plus years but not accepted when applying for a retirement visa.
I just had mine extended, they gave me 30 days from the expiry of the original 30 days, I still had 5 days to run on my original entry. I was under the impression that it started from the day it was given but not so this time.