A directive has been sent to all immigration officials stating that Thai nationals who enter Thailand on a foreign passport are no longer treated as foreign nationals for immigration purposes and that they can come and go as they please, without restrictions, on foreign passport so long as they also have proof of Thai nationality (for instance an ID card.
This brings to an end the perverse situation of many Thais (for whatever reason) entering Thailand on a foreign passport and being treated as a foreigner for immigration purposes.