JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
  <ul class="menu">
    <li>
      <a href="#">Top Level Link 1</a>
      <ul class="submenu submenu-1">
        <li><a href="#">Submenu 1 Link 1</a></li>
        <li><a href="#">Submenu 1 Link 2</a></li>
        <li><a href="#">Submenu 1 Link 3</a></li>
        <li><a href="#">Submenu 1 Link 4</a></li>
        <li><a href="#">Submenu 1 Link 5</a></li>
      </ul>
    </li>
    <li>
      <a href="#">Top Level Link 2</a>
      <ul class="submenu submenu-2">
        <li><a href="#">Submenu 2 Link 1</a></li>
        <li><a href="#">Submenu 2 Link 2</a></li>
        <li><a href="#">Submenu 2 Link 3</a></li>
        <li><a href="#">Submenu 2 Link 4</a></li>
        <li><a href="#">Submenu 2 Link 5</a></li>
      </ul>
    </li>
    <li>
      <a href="#">Top Level Link 3</a>
      <ul class="submenu submenu-3">
        <li><a href="#">Submenu 3 Link 1</a></li>
        <li><a href="#">Submenu 3 Link 2</a></li>
        <li><a href="#">Submenu 3 Link 3</a></li>
        <li><a href="#">Submenu 3 Link 4</a></li>
        <li><a href="#">Submenu 3 Link 5</a></li>
      </ul>
    </li>
    <li>
      <a href="#" class="active">Top Level Link 4</a>
      <ul class="submenu submenu-4">
        <li><a href="#">Submenu 4 Link 1</a></li>
        <li><a href="#">Submenu 4 Link 2</a></li>
        <li><a href="#">Submenu 4 Link 3</a></li>
        <li><a href="#">Submenu 4 Link 4</a></li>
        <li><a href="#">Submenu 4 Link 5</a></li>
      </ul>
    </li>
    <li>
      <a href="#">Top Level Link 5</a>
      <ul class="submenu submenu-5">
        <li><a href="#">Submenu 5 Link 1</a></li>
        <li><a href="#">Submenu 5 Link 2</a></li>
        <li><a href="#">Submenu 5 Link 3</a></li>
        <li><a href="#">Submenu 5 Link 4</a></li>
        <li><a href="#">Submenu 5 Link 5</a></li>
      </ul>
    </li>
  </ul>
</nav>

CSS

body {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  min-width: 1280px;
}

a {
  color: #000;
  text-decoration: none;
}

a.active {
  color: #f00;
}

ul {
  margin: 0;
  padding: 0;
}

ul li {
  display: inline-block;
}

.menu > li {
  position: relative;
  font-size: 18px;
}

.menu > li + li {
  margin-left: 100px;
}

.submenu {
  position: absolute;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  flex-direction: row-reverse;                   /* NEW */
}

.submenu-4,
.submenu-5 {
  right: 0;
}

.submenu li {
  font-size: 14px;
  white-space: nowrap;
}

.submenu > li + li {
  margin-left: 25px;
}

a:not(.active) + ul {
  display: none;
}

.submenu-4 > li:nth-child(1) { order: 5 ; }        /* NEW */
.submenu-4 > li:nth-child(2) { order: 4 ; }        /* NEW */
.submenu-4 > li:nth-child(3) { order: 3 ; }        /* NEW */
.submenu-4 > li:nth-child(4) { order: 2 ; }        /* NEW */
.submenu-4 > li:nth-child(5) { order: 1 ; }        /* NEW */