You can directly bind Chocolat to <a> links, when clicked the lightbox will open.
<div>
<a class="chocolat-image" href="img/a.jpg" title="image caption a">
A <!-- you can display a thumbnail here : <img src="thumb/a.jpg" /> -->
</a>
<a class="chocolat-image" href="img/b.jpg" title="image caption b">
B <!-- you can display a thumbnail here : <img src="thumb/b.jpg" /> -->
</a>
</div>
Chocolat(document.querySelectorAll('.chocolat-image'), {
// options here
})