Thirty years ago, Mana Treelayapewat told his friends that when had children, he would sing the song Saeng Dao Hang Sattha (Starlight of Faith) as a lullaby.
Saeng Dao Hang Sattha was written by socialist intellectual Jit Phumisak and was popular among student activists during the 1973–1976 political uprising.
The first time Mr Mana sang the song to his eldest son was 16 years ago, when he was born. On Thursday, he sang the song with his son at the Central Juvenile and Family Court as the boy faced a charge for attending a political protest in October.
Violating Section 112 -- the lese majeste provision of the criminal code -- carries up to 15 years imprisonment. It is used against people suspected of defaming, insulting or threatening the kingdom's royal family.
Mr Mana says he and his wife will stand by their son throughout this difficult time.
They hope that no other family will have to endure the same pain their family is now going through.
The father posted a Facebook message expressing his feelings about the serious charge pressed against his son. He said his entire family is hurt and worried about the young activist.
Although Mr Mana does not agree 100% with his son's political views, he encourages his son to have freedom of thought.
As for his son's case, he wrote he will leave the fate of his son to the judicial system.
Mr Mana's son is accused of joining an anti-government march on Silom Road in Bangkok on Oct 29. He is said to have worn a sleeveless top with a message that mentioned the name of His Majesty the King.
The 16-year-old faced a lese majeste charge after Warissanan Sribowornthanakit, a royalist, filed a complaint against him and Chatuporn Ung, 23, another activist, with Yannawa police.
The couple accompanied their son when he turned himself in on Thursday, to acknowledge the charge. He was taken to the court for questioning before being released on bail.
"As his parents, the best thing we can do for our son during this difficult period is to hold hands and walk through this ordeal together," Mr Mana wrote. "As his father and mother ... we absorb his pain as much as we can."
He said he has one wish, which arises from what is happening to his family.
"I hope this painful experience will stop with this family," he said. "Do not let it happen to others.