Shade on top covering the entire carriage and protective braces in the front are definitely plus points. But I noticed some disadvantages too.
Since the driver sitting on the bicycle part is on the edge of the structure, line of action of the driving force should also be along that edge and put a sheering stress on the overall structure. This is a big structural flaw, I wonder how often the welding at the joints between the bicycle and carriage breaks.
I guess total mass of trishaw should be less than the Bangladeshi rickshaw - that's a good advantage. But asymmetrical shape, implying less maneuverability, undermines that advantage. Imagine two passengers (or one very fat one) sitting in the carriage of a trishaw going in quite high speed. If driver clenches on the break, the trishaw would rotate uncontrollably since the carriage would have more mass and inertia would cause it to keep moving. Might just flip it over as well.
Despite these disadvantages, this vehicle has survived and carried people on Malaysian streets for several centuries. The design must be quite appropriate for the Malay traffic. But to verify that we need to dig deep into history and perform a proper anthropological study for which I'm afraid I don't have enough information or education. So this curiosity has to take it's place at the back of my head for the time being.