Lead arm jab stepping forward, as you bring back leg up follow with side elbow strike, from the following arms angle across to the point you almost hit. This will make them think that is your primary target. At this point you should be less than a foot away, and if you even flinch in the direction toward that point, because its to the head, they will think you are going for it... again. Instead, as soon as you see them react in a way to your feint, I would roundhouse, or knee them to the ribs.
Because I'm small, what muai thai techniques I employ are usually only viable when combined with deceit.
Another favorite I use it back-leg crescent kick to the arm, clearing them, you then step across and use the torque for your back leg to deliver a very harsh kick to either their neck or head.
Those are two combinations which might work. Remember, when it comes to fighting, all plans tend to fall apart save the simple ones. My simplest rule is the one which keeps me safest is 'Don't be there. If not there, the strike can't hurt you.' and frankly, it works. However, this is the opposite of what you'll encounter as a muai thai practitioner, who are much more direct in both their attacks, and their defenses. Unfortunantely the style of Muai Thai I learned was badly corrupted by both kick-boxing, TKD, and weirdly Irish boxing. Don't ask me why, I can only assume it's because he's from Britain and because he was a green beret during the korean war. He has since retired also. Quite honestly I greatly question if what he taught was muai thai at all, but when I use the kicks Im generally told what ive just done is. You never know sometimes, so take care that the technique you use is muai thai. I've seen a few people who practice it whose kicks are actually TKD kicks as opposed to what they think, or are trying to do.