SINGAPORE - Indonesian President Joko Widodo and First Lady Iriana flew economy class into Singapore on Friday with a 10-men entourage to attend his youngest child's graduation ceremony at Anglo-Chinese School (International).

The two, accompanied by Indonesia's ambassador to Singapore Andri Hadi, proudly watched their youngest son Kaesang Pangarep, 19, go onstage on Friday evening to receive his certificate for completing his International Baccalaureate diploma at ACSI.

He was among 146 receiving certificates at the ceremony attended by an audience of some 600, including parents, school staff, embassy and security officials.

Kaesang is the youngest of Mr Joko's three children; the 53-year-old president has an older son, Gibran Rakabuming, 27, and a daughter Kahiyang Ayu, 23.

Ms Kahiyang had flown in earlier in the afternoon to support her brother and handed him balloons after his graduation.

"I am very proud of him and have motivated him throughout his time here," she said shyly.

Mr Joko said he was "very happy" to be able to attend the graduation and see his son. "I feel happy and I wish to say thanks to ACSI for helping to teach my son." He said he had sent his son to school overseas to train him to become independent.

Asked what he advised his son to do, he said: "He said last year he wanted to go to SMU (Singapore Management University) but I don't know."

Kaesang received the loudest cheers from his excited schoolmates during the ceremony. Mr Ho Wee Kwong, Kaesang's physics teacher, said his student remained humble throughout.

"No one knew his status (as the son of the Indonesian president). He takes the bus just like the rest of the students. Even with teachers, he didn't say he's the mayor or the governor's or the president's son, " said Mr Ho, 40.

"He just says he's Kaesang and his father is a businessman, " he added.

The youngster said he felt motivated by his father who would call to give him advice and spur him on. "He says always pray to God," said Kaesang.

Asked what was next, the teenager said:"I haven't discussed with my father.... but maybe business management."

Asked if this was influenced by his father, who ran a furniture business, he added with a smile: "No, I am Influenced by myself."

His excited schoolmates swarmed the president who entertained their requests to take pictures and selfies with them.

According to Mr Joko's spokesman, Cabinet Secretary Andi Widjajanto, the president refused to use his presidential aircraft for his trip because the purpose of his visit was personal.

"It's a personal trip so no ministers or officials are in tow. Pak Jokowi will travel as Joko Widodo, not as President," he told reporters, referring to the president using his nickname.

Mr Joko's eldest son, Mr Gibran, also went to school in Singapore, graduating from the Management Development Institute of Singapore in 2007 before attending the University of Technology in Sydney. He now owns and runs Chilli Pari, a Solo-based catering service.

Ms Kahiyang, who graduated from Sebelas Maret University in Solo last year majoring in food technology, is waiting to enter the civil service in Solo.

Mr Joko is the latest serving Indonesian president to have children studying in Singapore.

While he was in office, former president Susilo Bambang Yudhoyono's two sons, the elder Agus Harimurti and the younger Edhie Baskoro, both graduated from S Rajaratnam School of International Studies (RSIS) in 2006 and 2007 respectively.

Graduating in the same year as Mr Agus was Mr Loro Horta, son of former Timor Leste president Ramos Horta, and Mr Nguyen Minh An, son of Vietnam's former President Nguyen Minh Triet.

Mr Joko's spokesman said the president will stay overnight in Singapore before flying back to Jakarta on Saturday.

zubaidah@sph.com.sg