As a frequent user of the express, both from Payathai and Makkasan, I would prefer that the Payathai and Makkasan express trains were joined, so they leave every 20 minutes from Payathai and stop at Makkasan, than to leave each of these stops exclusively only every 40 minutes. It is so frustrating to arrive at either station, to find the train has just left and you need to wait a whole 40 minutes, and could result in missing a flight.