Those are for the railway line crossing and positioned after the 3240 crosses each respective lane of the Railway Road. If they were to stop traffic as you imply they would be positioned before the junction.
For all of the main junctions crossing the railway line road, the road to/from Sukhumvit has precedence. (The Khao Noi crossing is a bit confusing because there's an extra set of signs before the road Railway Road meaning no-one apparently has right of way, but nevertheless that's not the case here).