Two Thai teachers have been suspended for allegedly piercing schoolchildren's lips with a pin as a punishment for chewing gum in class.

The unnamed female homeroom teacher, 27, became angry when she stepped on a piece of gum on the floor at the Wat Dan Samrong School in Samut Prakan, Thailand, on January 25.

When no pupil would admit to spitting out the gum, she called a senior teacher, 50, who then punished the 36 schoolchildren by having them perform a bizarre 'vow ritual'.

The woman lit some incense and made the pupils 'take a vow' before stabbing their lower lips with a single safety pin.

Furious parents filed a report with the police and slammed the school administration when the kids came home that day crying that they had been hurt in class.

School director Apicha Petchnoi said both teachers have been suspended and investigations into the incident were ongoing. The teachers were not named by police.

Police Colonel Praphas Mangkang, deputy commander of the Samut Prakan Provincial Police, said officers were called to attend a meeting between school staff and parents on January 26.

He said: 'The school has acknowledged the teachers' actions and said that all students would be sent to the Samrong Hospital for health checks. We are also planning to question teachers and the guardians to see if there are grounds for filing assault charges.'

He added that the school has agreed to shoulder medical expenses, while the Ministry of Social Development and Human Security will hand out financial compensation to the parents.

Outraged mum Inthira Jonjenka, 28, said: 'We parents want the teachers to be punished and to hear a direct apology from them. We want them to resign and never teach again instead of merely facing suspension.

'This is not the first time they were reported for severe corporal punishment at school. If they are suspended, we can prevent incidents like this from recurring.'

Meanwhile, Am, 30, the aunt of one of the pupils, said: 'When I heard about it from my nephew, I was shocked. How could you punish children like that? I called the school, but I was just told to be patient and have my nephew tested for infections at the hospital.'

A committee has been established to investigate the matter. The findings will be submitted to the Samut Prakan Primary Educational Service Area Office, which will mete out official sanctions.