Waiting almost three hours to get a bank letter today to go immigration tomorrow for an extension (Samut Prakan) I did not notice until I got home that they spelt my first name wrong and stuck an extra R in it. Will immigration reject it if they notice, or is it best to do the Bank all over again?

They may not notice it or let it go if is a obvious typo let it go if every thing else is correct. I think I would give it a try.