HAT YAI, Aug. 10 -- A secondary school in southern Thailand with about 3,600 students has been forced to close for two days after a sacked foreign teacher allegedly posted gun-related images and threatening messages aimed at the school community.

Hatyaiwittayalai School in Songkhla province will keep its gates shut on Monday and Tuesday, with lessons moving online as a precaution, the Bangkok Post reported.

School director Thitiwit Meechooworapong announced the closure on Saturday night, saying it was intended to protect students, teachers and other employees.

The decision followed alleged threats by Pieter Johannes Dreyer, a former English-language teacher in the school's English programme.

Police said Dreyer, a South African nationa...