Positioning of under the Material-ui component

Use MenuProps attribute of Select element

<Select
    MenuProps={{
      anchorOrigin: {
        vertical: "bottom",
        horizontal: "left"
      },
      transformOrigin: {
        vertical: "top",
        horizontal: "left"
      },
      getContentAnchorEl: null
    }}
>
    <MenuItem value={10}>Ten</MenuItem>
    <MenuItem value={20}>Twenty</MenuItem>
    <MenuItem value={30}>Thirty</MenuItem>
</Select>