Sudin used to serve as a senior officer at the Border Security Agency (Aksem), the government body responsible for guarding the entry and exit routes at the country's frontier.
He spent time at the entry points in Perlis and Kelantan, and served in Thailand for several years before his mandatory retirement in 2019.
For 30 years, he carried out his duties including overseeing his officers and members to ensure that they were on top of their own responsibilities.
Speaking to MalaysiaNow, he recalled how he had ordered the transfer of one of his men who was being investigated for corruption.
He also appeared as a court witness in Perlis once, to testify about the corrupt practices of one of his members who was involved in smuggling illegal goods across the border.
"I gave my full cooperation," he said. "But I had to guard the reputation of my team.
"One or two of my men might have been involved in trouble, but I could not allow my entire team to be called corrupt. That wouldn't be fair, because the rest of them were honest in carrying out their duties."
Aksem has since been disbanded with border control duties now under the jurisdiction of the police, but Sudin remains firm in his stand on corruption in the civil service – a longstanding issue which reignited after a minister's claim of graft at the country's entry points.
Tiong King Sing, the tourism, arts and culture minister, became embroiled in controversy following reports of his intervention in the detention of a Chinese national at KLIA.
He also hit out at immigration officers at the airport, accusing them of corruption and power abuse.
Veteran political analyst Ahmad Atory Hussain said corruption in the civil service had been a known issue for a long time.
He said talk had swirled on the matter even during the administration of previous governments.
But he also warned that the recent uproar would continue to tarnish the government's image in the public eye.
"This is why the prime minister will be careful when issuing statements on this, because he doesn't want to damage the image of the government or the immigration department," he said, referring to Anwar Ibrahim's surprise visit to KLIA after the incident with Tiong.
"Here, it is the court that will decide who is right and wrong."
Civil service vote bank?
The civil service has long been seen as a government vote bank, with Defence Minister Mohamad Hasan expressing confidence earlier this year that the military would back Barisan Nasional (BN), a component of the coalition government, at the upcoming state elections.
Elections are due in the states of Selangor, Negeri Sembilan, Penang, Kedah, Kelantan, and Terengganu, where voters will head to the polling booth on Aug 12.
Atory said it was a norm for defence ministers to announce the support of uniformed bodies such as the military and police for the government.
"This has more to do with psychological warfare," he said.
"Of course he wouldn't announce that they support the opposition."
Still, upsets happen such as in the Sungai Udang constituency in Melaka where the army vote was credited with a swing in support away from BN and towards Perikatan Nasional at the state election in 2021.
Acknowledging such shifts, Atory said the question now was where Mohamad had obtained the data predicting that the army would support BN and its partner in government, Pakatan Harapan.
"I don't recall any studies that have said this," he added.