In a statement, the commission said that this is to test the quality mobile phone signals and operators can be notified promptly in case of any disruption.
Thakorn Tanthasit, the NBTC Office secretary general, said that signal quality can be properly checked in areas where a large number of mobile users gather.
"The trucks are to test the signal, not to cut off the signal in the areas," he said.
Earlier, mobile phone operators were told to increase capacity in protest areas, to cope with the rising voice and data transmission.