Just to add my report - Last Thursday arrived BKK and caught a taxi at around 5 p.m. to the Royal Orchid Sheraton. Asked the taxi driver for the meter, and he agreed and said, "You pay airport and highway" and I agreed, as well.

At the first toll booth, the meter read 18 km and 133 THB. I handed the driver the 25 THB for the toll when he asked for it.

At the second toll booth, the meter read 24.2 km and 171 THB. Paid the 45 THB toll to the driver.

Arrived at Royal Orchid Sheraton - 33 km and 237 THB on the meter. Add the 50 for the airport, and I gave him 300 THB and told him to keep the change.

We encountered about 15 minutes of stop-and-go traffic along the way, and one really long stoplight.