I was in Udon Thani area back in 1972 - 1973. The main road through town and the highways traveling in Thailand were paved then. Almost no other road/street was. All the bungalows had chairs or benches for those that wore laced up shoes or boots.
Removing laced up shoes or boots was a pain during the dry season, but was a necessity during the rainy season. Otherwise, you tracked mud inside.
We never removed boots when entering communication vans or trucks. It was a pain having to mop them out nearly every day during the rainy season. At least in the trucks we could hose the mud out without concern for water sensitive electronic equipment damage. Sometimes there was so much mud tracked into the comm vans on our boots, we used a shovel to scoop some of it out.
I remember this as the reason, both in Vietnam and Thailand, as the reason for removing shoes when entering places. Not for hygienic reasons, for muddy reasons.
Even here in the U.S. of A., there were houses built with "mud rooms" for the same reason, to remove footwear so as not to walk mud into the house. I live in a 71 year old house and it has a storm door, mud room, and then the entry door.