Bangkok is served by the port of Laem Chabang, but isn't itself a cruise port. Together, the port of Laem Chabang functions as the point of embarkation for just one sailings every year from Norwegian to Asia.
On average Bangkok is moderately expensive compared to other ports. Check the diagram below for the average cost per day by month (Cruises only depart from Bangkok between February and February). Prices are around steady throughout the year.