@Nongnuch *******
No, the stay granted by the visa is an independent right that continues even after the visa itself has expired, provided you were stamped in beyond the visa’s validity period. However, you lose your right to re-enter once the visa expires. So, if you leave without having physically purchased a re-entry permit, you will not be allowed back in, and the remaining stay will be cancelled. This is very technical, though. I don’t think we should make too much of a point about it now, as it may confuse the OP.