I had a similar thing with a delivery van after going to Cambodia on a visa run. It took ages if you weren't the first on or off. The second time I got out as soon as we got back to Pattaya and got on a motorbike taxi. Without luggage of course.

The true savings on the bus/van,at 400 Baht quoted above, is actually only 600 Baht as a pre-booked taxi is 1000 Bt.