Keep in mind that once you are granted with a 1-year visa stamp on your passport and you plan to travel out of Thailand within the span of your visa validity, you will need to get a re-entry permit to avoid getting your visa cancelled when you get back to Thailand.
A (Single Re-Entry Permit) is valid as the name suggest for a single use, whereas for a (Multiple Re-Entry Permit) can be used for multiple times in and out of Thailand and your visa validity stays as it is.
A person can apply for the re-entry permit in any immigration office or at the international airport before going out of Thailand.
