Thotsaphon Thananonsophonkul, 67, a retired university lecturer, has been handed a six-month jail term and a 20,000-baht fine for assaulting political activist Srisuwan Janya. The jail term was suspended for one year.
Mr Srisuwan on Thursday updated his Facebook account following the ruling of Don Muang Kwaeng Court on Tuesday.
Thotsaphon punched the political activist in the mouth on May 11 at the Election Commission's office, which is part of the government office complex on Chaeng Watthana Road.
Prior to the assault, Mr Srisuwan was giving a media interview about a complaint regarding Pheu Thai's 10,000-baht digital wallet policy.
Mr Srisuwan reportedly filed a complaint with Thung Song Hong Police against Thotsaphon for physical assault and defamation before prosecutors filed a lawsuit with Don Muang Kwaeng Court against him under Sections 91, 295 and 393 of the Criminal Code.
Mr Srisuwan wrote that the court found Thotsaphon guilty of violating Sections 295 and 393 of the Criminal Code for causing bodily harm to others and a misdemeanour.
As the defendant committed several offences, the court ruled to punish him according to Section 91 and handed down a six-month jail sentence and a 20,000-baht fine.
Due to his confession, the court suspended Thotsaphon's jail term for one year.
Failure to pay the fine will be punishable according to Sections 29 and 30 of the Criminal Code.
In addition, Thotsaphon must pay compensation totalling 50,420 baht to Mr Srisuwan with 5% interest each year until the payment is completed.
"This will be a lesson for those who act beyond the law," Mr Srisuwan posted in a message on his Facebook account.