Molotov cocktails are hurled at the tyres to keep them burning; the resultant smoke from the burning tyres prevent the security forces getting a clear view of the "Red Shirt" barricades further down Rama 4.
<a href="//commons.wikimedia.org/wiki/User:Takeaway" title="User:Takeaway">Takeaway</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>