def METHOD_NAME(self, name, calendar=None) -> Optional[date]:
    """
    Add Khao Phansa.
    Start of Buddhist Lent (also written as Khao Phansa Day) is a Buddhist
    festival celebrated on the 1st Waning Day of Month 8.
    Khmer variant: always fall on Month 8.
    Thai variant:  will use Month 8.8 instead for Athikamat years.
    https://en.wikipedia.org/wiki/Vassa
    """
    calendar = calendar or self.__calendar
    return self._add_thai_calendar_holiday(
        name, self._thai_calendar.khao_phansa_date(self._year, calendar)
    )