JSFiddle - React, Tailwind, and code Playground

HTML

<div class="balao">Oi!</div>

CSS

html, body {
    background-color:#eee;
}

.balao {
		float:right;/* ou float:left, vai do seu uso */
    color:#fff;
    background-color:#37688D;
    border-top:10px solid #37688D;
    border-left:10px solid #eee;
    padding: 0 10px 10px 10px;
}