For those who want to know...........
The Singapore TA-4S was created out of two single seat B's so the engine (J-65) could stay the same with the rest of their fleet. The length and cockpit arrangements were the same as any other TA-4, but in place of the long one piece canopy, the RSiAF wanted better over the nose visibility for the backseater and again to keep a common parts theme, the rear canopy as delivered was the same as the front unit (albeit with a different rear windscreen).
About the time the T/A-4SU project started, the bulged sided rear canopy was developed and installed.