Do I need to render a salute to an officer when my hands are occupied?

Good morning, afternoon or evening sir...while moving very quickly. Do not flinch or hesitate. No worries.

I was in San Antonio at Lackland AFB and, while walking over to the dispensary, I happened on a captain who was loading something into his trunk (with his head in the trunk). Unsure of the protocol, I did salute him. He returned the salute with his head still in trunk. Better safe than sorry

Second time? The adage that comes to mind is, "Burn me once, shame on you; burn me twice, shame on ME."

At least in the sea services there is no saluting indoors unless under conditions requiring you to wear headgear.

This is plainly a power move by the CSM, the Regulation plainly states that if both your hands are occupied and you walk past an Officer you still greet them by rank or saying a greeting of Good morning Sir /ma'am and continue on your way. If either the CSM or the Officer say's anything to you, their out of line and you should tell them in a respectful manner of the Regulations regarding Saluting of an Officer.

It is really an elementary answer. We follow the chain of command for good reasons, senior NCO's to basics, may not "like" saluting but respect the rank and traditions! 1st time could be an oversight, 2nd time was a choice! If you do not have pride in the uniform you wear, seek life elsewhere!

In the Marine Corps we were required to stop, drop what one was doing stand at attention and salute. If you were walking past an officer and both hands were occupied some Marines at the time would greet the officer and if he saw the situation he would more times than often say, "as you were" which meant continue as your were no need for a salute. If you were occupied as a group in a work activity and an officer came upon you the first Marine to see the officer calls for Attention! All snap to attention and the senior NCO will salute for the group. If you do not recognize his presence he'll usually state, "as you were" and no salute is rendered. Now this was the 'ol Corps back in the '60's. It may not be this way now. But knowing the Corps, tradition is a big thing. Semper Fi all.......

The short answer is no.
https://www.youtube.com/watch?v=zE5EE335khs

Years ago, I was walking downstairs outside my building while carrying a stack of books in my left arm and holding the handrail with my right hand. A lieutenant was standing at the bottom, and my first thought was that he was allowing me to descend before walking up himself. Nope. He was standing there waiting for me to render my hand salute (which I did once I got off the steps), and scolded me for not saluting sooner. I pointed out that I was holding onto the handrail for safety, and he said I should have taken my hand off to salute. So, I patronizingly asked him if he wanted me to risk my safety in order to salute. He asked for my unit, and went to see my First Sergeant. The first words out of 1SG's mouth: “What did SGT Pepper do this time?” That blew the wind out of the lieutenant’s sails. Funnily enough, the LT and I became friends later (and he had the opportunity to ask: “What did SGT Pepper do this time?”).

To answer your question: can you balance the mug on top of the binder? It doesn't matter what AR 600-25 states; the CSM outranks you by so much that he wins. Most people won't get angry as long as you make some effort.

Usually a "by your leave" will suffice unless the officer is a nugget then all bets are off.