The Port Authority of Thailand (PAT) and its labour union in separate statements have urged exporters and shippers to divert their shipments from the port in Klong Toey to other sites.
There are fears that the ongoing political turbulence might disrupt operations at Bangkok Port, where services were suspended three days last month as union members showed their support for the anti-government People's Alliance for Democracy (PAD).
On Tuesday, the Thai National Shippers Council alerted its 2,700 members about the threat of industrial action and advised them to divert shipments to Laem Chabang from next week.
Despite higher costs, exporters have opted to use Laem Chabang to avoid the risk of failing to meet shipment schedules and of damaging their reputation among foreign buyers, said the TNSC.
Bangkok Port can service 40,000 containers per week, accounting for about a quarter of the country's capacity.
Shippers estimate an extra cost of around US$88.35 to $117.8 for moving each container from Bangkok to Laem Chabang.