Haven't heard many people talk about the taxi ride between the 2 airports.

In my case, our NOKAir flight was cancelled (as it turns out, they grounded a few planes until they were fully checked out. This was a few days after the 1-2-Go crash). In the afternoon I got a SMS to my phone that the flight was canceled, the re-booking options, times, and phone number to call.

We missed the last flight from DMK, because of traffic issues in BKK (100 minutes to cover a few kms to the expressway).

At DMK, we convinced them to let us fly from BKK, that we would pay the taxi.

I don't remember the exact meter price.
We must have hit 4 toll booths.
distance was 46km
time from DMK to BKK was 50 minutes (all on tollway roads/ no traffic jams)