More than 100 spikes were missing from the track between Ban Thepha and Ban Koh Saba stations in Thepha district.
After an inspection, police said the spikes were not likely to have been removed at the same time for insurgency attempt because each of the missing spikes were wide distances apart from each others. Most of the locations they were missing were near railway crossings.
Some spikes were missing for a long period and they were not removed on both side of the tracks.
Although the missing spikes did not affect rail services, engineers from the State Railway of Thailand (SRT) would inspect the track and fix the missing spikes.
In a separate development, Songkhla governor Krisada Boonraj has ordered security measures stepped up in the province as insurgent groups may stage violent attacks to mark the tenth anniversary of the Krue Se incident.
Security officers were on high alert, checkpoints were set up to inspect vehicles or suspicious persons.
Monday marks the 10th anniversary of the April 28, 2004 Krue Se incident in which 32 people were killed in clashes between authorities and suspected insurgents at a Pattani mosque.