When returning to Thailand from an out of country vacation, and having a NON-O A multi entry visa, what should the ADMITTED UNTIL date be in the stamp from immigration when returning to Thailand?  (one year, 90 days, or the date the original visa expires?)  If a date that is put in the stamp is far later than the expiration of the original visa, does it change the expiration date of the visa?

If entering using a Non 'O-A' visa you'll get permission to stay for 1 year.

 

The 'enter before' date is the expiry date of the visa and the last day you can enter to receive a new 1 year permit to stay.

 

The expiry date ('enter before') of the visa never changes.

Edited January 20, 20179 yr by elviajero

If you want the maximum from an OA Visa, exit and re-enter the Kingdom a couple of days before the "enter before" date on your Visa for an extra year.

You will need a re-entry permit (single or multiple) from an Immi office to keep the last year alive if traveling outside the Kingdom.