Philippine President Rodrigo Duterte to 'be on best behaviour' in Singapore

Controversial Philippine President Rodrigo Duterte may contain his signature colorful language when he arrives in Singapore for a two-day state visit on Thursday.

Like the U.S., Pope Francis and countless others, the Southeast Asian nation has also been a victim of the President's verbal tirades. Last year, the 71-year old recalled how he burned a Singapore flag in 1995 to protest against the execution of a Filipina maid.

Philippine President Rodrigo Duterte greets members of the Filipino community in the Cambodian capital of Phnom Penh on December 13, 2016.
Tang Chhin Sothy | AFP | Getty Images

"F*** you...You are a garrison pretending to be a country," he said in a Nov. 2015 speech, referring to the city-state.

Singapore doesn't take too kindly to insults. In the past, the country's leaders have sued and won damages or out-of-court settlements from foreign publications, including the International Herald Tribune, Wall Street Journal, Bloomberg and The Economist, for defamatory allegations.

Duterte, who met with Cambodia's government early this week, isn't expected to apologize for his remarks, but he may be extra-cautious on this trip.

"I expect him to be on his best behavior in Singapore," said Murray Hiebert, Southeast Asia specialist at the Centre for Strategic and International Studies.

The bilateral visit is aimed at expanding business ties, deepening defense and security cooperation as well as discussing key issues facing the region, so "having fruitful discussions in these areas will require that he not set his interlocutor teeth on edge with abusive name calling," Hiebert added.

Duterte will also be holding a session with Singapore's Filipino residents on Friday, a common practice of his when traveling abroad. There were an estimated 140,000 Filipino workers in Singapore last year, according to Philippine statistics, many of whom are employed as domestic helpers. Cases of maid abuse are all too frequent in the nation—in March, a Singaporean couple faced charges of failing to adequately feed their Filipina maid—and given Duterte's remarks in the past, it's a topic he may raise.

Though the President tends to be the most colorful on his overseas trips, especially when giving speeches to overseas Filipino workers, it's unlikely he will mar his first visit to Singapore by controversial tirades against the island-nation, noted Malcolm Cook, senior fellow at the ISEAS-Yusof Ishak Institute, a think-tank specializing in Southeast Asia.

Don't take Duterte literally: Philippines' government spokesman
Don't take Duterte literally: Philippines' government spokesman
Don't worry, Duterte is in tip-top shape: Philippines official
Don't worry, Duterte is in tip-top shape: Philippines official
What explains the Philippines' economic realignment?
What explains the Philippines' economic realignment?

While the President has attracted criticism overseas—human rights activists have accused him of state abuse over the extrajudicial killings from his narcotics crackdown—he remains immensely popular among Filipinos, who praise him for tackling a key source of crime and violence. Nearly 6,000 have died since the war on drugs began in July, out of which 3,841 were vigilante-style killings, according to new Philippine police data on Monday.

On Monday, Duterte shocked the world yet again after hinting that he personally killed criminal suspects during his reign as Davao City mayor, corroborating similar statements made throughout his presidential campaign. In December last year, he told a local radio station that he shot three kidnappers in 1998.

People should not overreact to his comments, insisted the man tasked with the tough job of heading Duterte's public relations team.

"The President talks like that, we should not take his comments literally because he wants to instill fear in the minds of criminals," Martin Andanar, secretary of The Philippines' presidential communications office, told CNBC's "Street Signs" on Thursday. When listening to the President's remarks, the public needs to read between the lines, he continued. "In one to ten of the President's speeches, there are maybe five that you need to decipher."

With no concrete deals expected on this Singapore trip, foreign policy could feature prominently on the agenda.

"Singapore will likely be very interested in Duterte's policy, particularly towards the U.S. and China," said Cook, referring to the Philippine leader's efforts to distance himself from Washington and cozy up to Beijing.

The Philippines will also be chairing the Association of Southeast Asian Nations (ASEAN) bloc next year, followed by Singapore in 2018, so discussions on regional diplomacy are also likely.

"Presumably, there are concerns in the region of a more inward-looking U.S. foreign policy in the coming years under President-elect Trump, so leaders may prioritize strengthening defense ties," explained Kevin McGahan, political science lecturer at National University of Singapore.

In Phenom Penh on Tuesday, Duterte announced that old age and health issues, which range from migraines to Buerger's disease, might prevent him from finishing his six-year term. But Andanar dismissed those fears on Wednesday, noting that the President was "in tip-top condition and in the pink of health."

—Follow CNBC International on Twitter and Facebook.