<table>
  <thead>
    <tr>
      <th style="width:15%"> TH1 </th>
      <th style="width:25%"> TH2 </th>
      <th style="width:20%"> Lorem ipsum, dolor sit amet consectetur adipisicing elit. Provident quas deleniti similique! Quam atque pariatur fugit, sapiente voluptatibus natus, libero esse beatae recusandae, eligendi quas! Dolores reiciendis ullam omnis odio. </th>
      <th style="width:20%"> TH4 </th>
      <th style="width:20%"> TH5 </th>
    </tr>
  </thead>
</table>

table {
  width: 100%;
  table-layout: fixed;
}
th {
  border: 1px solid red;
}