I wrote a breakdown on this a few months ago:
The first thing to understand about fighting in the open guard is understanding the footwork.
You will often be advised to circle away from your opponent’s lead hand. In an open guard match, this means that the orthodox fighter needs to circle in the direction
opposite of his normal movement. This prevents his opponent from circling headlong into the southpaw’s left hand and left body kick.
Stepping outside of the opponent’s lead leg to throw a rear straight is the best way to counter your opponents jab. When you step to the outside, you set in motion two actions:
- You bring your rear shoulder directly in front of your opponent’s face
- It shortens the path that the hand needs to take in order to find the chin
This also brings your opponent’s body closer to your rear leg. This means that your kick will meet your opponent’s gut in the middle of its arc. While a step in before a body kick is not necessary, it is certainly beneficial if you’re looking to pack more power into that kick.
Knowing when to step to the power side or step straight forward is mandatory for winning a fight in open guard. If you constantly step towards a southpaw’s right side, eventually he’ll use the opportunity to slam your spleen with switch kicks. Alternatively, he’ll let you step outside his lead foot and use that inside angle to land a lead hook.
(TL) Kaew Fairtex takes a deep step past his opponent’s lead leg and into his blind side.
(TR) This angle is only available in open stance match ups.
(BL) He uses this moment to catch his opponent with a left kick as they turn.
(BR) He then resets ready to exchange again.
Alternate Angles
Let’s elaborate on the inside angle. When a southpaw is looking to land a lead hook and wants to take an angle to do so, he has two ways of going about it:
- Take an outside angle, pivot around, and throw a hook from the opponent’s blind spot
- Step inside the opponent’s lead foot
The latter options brings the lead hand directly in front of the centreline, allowing the jab or lead hook to easily land without having to worry about a counter right. In boxing, this was how
Miguel Cotto decked Sergio Martinez multiple times.
When your opponent steps outside your lead foot in punching range, he will always
give up a potential inside angle to do so. This means that if you time it right, you can step straight in with a hook or jab.
The rest is here:
http://www.muay-thai-guy.com/dismantle-the-sneaky-southpaw.html