I'd book a ride with Mr T or similar, the driver will be waiting for you at the departure gate with a sign with your name on it.
Let the driver know that the motorway ends at Pattaya and Sukhumvit Road there is roadwork, you can't turn right, do a U turn just before and left exit, head north.
BPH, you are KING, they will wait, don't be too concerned, they like your money.