There’s a difference between surrender and defection.
Soldiers who surrender are afforded protections and retain ties to their countries. After hostilities resolve or if a prisoner transfer is arranged, they return to their country and generally do not face punishment. At least according to Geneva conventions on lawful war. It’s rarely this simple and clean.
Soldiers who defect have few, if any, protections and are in a weird place with nationality. They are typically considered fugitives by their home countries and may or may not be able to travel internationally as they may also be stateless.