Bangkok is served by the port of Laem Chabang, but is not actually a cruise port. Together, the port of Laem Chabang acts as the embarkation for just one annual sailings from Norwegian to Asia.
On average Bangkok is moderately expensive compared to other ports. Prices are roughly the same throughout the year. Look at the illustration below for the monthly average cost per day (Cruises only depart from Bangkok between February and February).