JSFiddle - React, Tailwind, and code Playground

HTML

<table>
  <thead>
    <tr>
      <th class="th">h1</th>
      <th class="th">h2</th>
      <th class="th3">h3</th>
    </tr>
  </thead>
  <tr>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr>
    <td>r2c1</td>
    <td>r2c2</td>
    <td>r2c3</td>
  </tr>
</table>

CSS

table {
  border-collapse: collapse;
  border-right: 0px;
  border: 1px solid;
}

td {
  border: 1px solid;
}

thead {
  border: 2px;
}

th.th {
  border: solid;
}

th.th3 {
  border-top: 1px dashed;
  font-weight: normal;
}