There is no time for your Hok Bong or other actions with the left hand. Your opponent has already pulled it down and is a beat ahead of you.
You have three options : 1) cross block with pak (not at all optimal but could save you from being KO'ed)
2) counter punch with the right hand. Now, if your right hand is coming from the right or center then the best you can hope for is a simultaneous knock out. However, if your right hand is coming from the left toward the opponent's center, AND THE OPPONENT HAS THROWN A STRAIGHT PUNCH, you can counter punch and defend together. If it's a hooking punch, however, you'll still get clocked.
3) hope you have the chin to take the shot
First it seems that the hand is there for this one (or similar) scenarios, at the expense of all the other scenarios where the position appears to less than optimal.
Second I am confused because, not you but others here, have constantly disparaged people who have given similar descriptions of other scenarios of "hand chasing" and this certainly appears to be just that.
All that said
@Danny T and
@Nobody Important together have the point.
A) (Nobody) you need to be willing to take a hit and in such a circumstance you will simply not have the time for the type of counter that is being suggested. So steel yourself and cover. A chuen sau (with the below) can be an excellent cover and since you are simply covering it isn't hand chasing.
B) (Danny and Nobody) what you need to do is use (my slang follows) "body english" and footwork. Iif it doesn't stop the strike it will at least bleed off some of the force of the blow and also change the line making the follow up strikes (the other hand is always coming) less effective as your opponent now has to change their line. "B", is often overlooked. All too often when foot work is spoken of it is through the lens of creating avenues of attack.
A simple relief or t-step is, more often than not, easier to execute than a counter because you can train it as part of the natural "flinch reflex". When executing this kind of foot work it, even if you get hit, the change of angle and nature of the movement also bleeds off force.
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It's all well and good to have as your goal/general philosophy "always forward" but there are times, as the hypothetical scenario give here illustrates, where you in essence need to cover and reset because the other option is hand chasing which has a much lower % of success.