I know many foreigners where it’s not a issue and they are in Bangkok. No amendments since April 2018. Did you read the whole article. The announcement came from Bangkok’s labor dept and it’s the law.
The only thing he is not correct on is he suggest to register the change. The labor department won’t accept the application to register the change of work as it’s no longer required to do so. They will just wave you away. “No need “
if they say that he is wrong ? Then that should be the end of it. If he fires you cause you don’t quit, then take him to labor court and get severance and any additional compensation.
Narmada Peiris your employer is dead wrong. Never been that case, having to quit your job to change positions. If he goes to the labor dept. they will tell him the same thing. It’s no longer required to change positions on your work permit or add positions.