Even if you could make the last ARL, I think finding a taxi at Makkasan would not be an efficient use of time. IIRC, it's quite a walk from the platform out to Ratchadapisek where you'd catch a cab towards Sukhumvit.

At Phaya Thai, the likelihood that a cab can be waived down from the passing traffic is OK.

I would take a taxi and skip the tollway. But, you can save a few bucks with the ARL.