import sys
import time
from PySide2 import QtCore, QtWidgets

class MyWidget(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        self.button1 = QtWidgets.QPushButton("isrun=false")
        self.button2 = QtWidgets.QPushButton("mythread.terminate")
        self.layout = QtWidgets.QVBoxLayout()
        self.layout.addWidget(self.button1)
        self.layout.addWidget(self.button2)
        self.setLayout(self.layout)

        self.button1.clicked.connect(self.setF)
        self.button2.clicked.connect(self.termThread)

        self.mythread = AThread()
        self.isrun = True

    def setF(self):
        self.isrun = False
        print("isrun = False")

    def termThread(self):
        self.mythread.terminate()
        print("thread stopped")


class AThread(QtCore.QThread):
    def run(self):
        while True:
            if widget.isrun:
                print("thread ping")
            else:
                self.terminate()
            time.sleep(1)


if __name__ == "__main__":
    app = QtWidgets.QApplication([])
    widget = MyWidget()
    widget.resize(800, 600)
    widget.show()
    widget.mythread.start()

    sys.exit(app.exec_())