But I don't have a letter. No instruction like this was given to me by my employer. They asked my date of departure. I told them. They said they would cancel accordingly.
So you're saying my extension stays valid until I cancel it or leave the country? My permit cancels in April. But my extension in my passport say I'm good till July. So technically, I could've stayed in Thailand till July with no problem? And no overstay fine either?
It is an extension of stay. And you're right, the employer cannot cancel the visa. They can only cancel the work permit. But I was told when the permit is cancelled, then the visa is automatically cancelled.