There is another serious syndrome beyond the luggage carousel one (read more here) that has infected many passengers at world airports.
Even when the Bangkok airport was close to empty last Saturday night, the passengers were able to block the moving walkway by standing all over. This is not unique to Bangkok unfortunately.
The correct way would be to stand on the right and let people to pass you on the left.
When you would like to pass a a group of people, you should approach them on the left and just say “Excuse me – on your left”. Even if they are not proficient in English, you are usually given way.
I understand that some people take their time and prefer not to walk on the moving walkway but then they should congregate on the right and let those that prefer to walk bypass them on the left. I usually do succeed using the “excuse me – on your left”, although some then just give space between people and not on the left.