Hi pLoskutov, I'm specifically referring to this segment: https://www.openstreetmap.org/way/555852322

While we're generally discouraged from using Google for mapping, the street view link below shows two signs related to a Department of Agriculture Cooperative estate and a Watershed Management unit, rather than a residential settlement. Hence 'highway=service' would be the most suitable classification in this case:

https://www.google.com/maps/@19.0595073,98.3151573,3a,29.4y,170.43h,75.68t/data=!3m6!1e1!3m4!1s90USCcsb8AZGvZSYnSRSCw!2e0!7i16384!8i8192?entry=ttu

I understand this might be a bit perplexing, but the designation "highway=unclassified" doesn't imply that the road is impossible to classify. Instead, it signifies that it's a road within the network hierarchy that holds lower significance compared to tertiary roads. In essence, it would have been more fittingly labeled as "quaternary."

You can find detailed information about this in our Thailand wiki, so please feel free to reach out if you have any additional queries.