Chalermsak Parathanya addressed almost 5,000 students on Tuesday, after young people gathered outside his office to protest and blow whistles on Monday.
The pupils were angry about being forced to march from school to attend a pro-election rally at the old provincial hall on Jan 17.
Many of the students said they disagreed with the activity and the march resulted in their school being branded the “pro-red shirt school” in the local area.
Mr Chalermsak explained that the school had earlier received a letter from the Learning Centre for Politics in Democracy, an agency under the authority of the Office of the Election Commission of Thailand, asking it to send two teachers to participate in a workshop as part of a parliamentary election awareness campaign in academic institutes.
The two teachers who took part in the workshop were required to hold an activity to promote elections in their school.
Mr Chalermsak said the school and its student council agreed to organise the demonstration to campaign for election democracy without the intention of supporting any particular political group.
He added that it is normal practice for the learning centre to organise educational activities relating to democracy when there is an election and said that the agency always seeks cooperation from the school, which is the biggest in the province.
He said the school did not want to prevent students from expressing their political opinions but hoped to encourage them not to use violent language to convey their views on social media.
Pupils and teachers who disagreed with the pro-election rally said the conflict had been resolved since they were satisfied with Mr Chalermsak’s explanation.