Soh Rui Yong, a two-time SEA Games marathon champion, has filed a defamation writ in the High Court against Singapore Athletics (SA) executive director Syed Abdul Malik Aljunied.
The High Court deals with civil cases where the claim exceeds $250,000.
Soh is suing Malik for losses and damages arising from the latter's alleged defamatory comments made in a Facebook post and remarks on that same post's thread on Aug 17.
The Straits Times understands that an indicative value of $500,000 has been provided, but that damages for libel, including aggravated damages, will be left to the court to assess.
In a post on his personal blog on Tuesday, Soh said his lawyers from Foxwood LLC had filed the writ as Malik had not responded to a legal letter sent to him on Aug 19.
That legal letter had demanded that Malik issue a public apology for his social media comments, undertake not to publish any further statements that may be defamatory and to compensate Soh for the "injury caused to his professional standing and reputation".
The spat between both parties was triggered after Malik posted a photo of himself with two children on Facebook. While he did not name anyone in his post and subsequent comments, Soh's statement of claim on Monday stated the former's comments were "false and defamatory" to Soh.
His lawyer's letter also stated Soh is an ambassador for eight brands and events and Malik's comments had allegedly caused "irreparable damage and/or injury to (Soh's) image and reputation" and allegedly exposed him to "hatred, contempt and ridicule".
Malik declined comment when contacted on Tuesday.
Soh, who won marathon golds at the 2015 and 2017 SEA Games, has been embroiled in disputes with the Singapore National Olympic Council (SNOC) and SA over his non-selection for the Nov 30-Dec 11 Games in the Philippines.
On Aug 19, Soh sent legal letters via his lawyers to both organisations. The 28-year-old accused the SNOC of breaching the "fundamental principles of natural justice" by not convening a hearing or giving him "fair opportunity to defend the allegations".
In a separate letter, he also accused SA of defaming him in its Aug 2 statement on the SNOC's decision.
Last week, Soh said he is willing to meet SA, which governs track and field in Singapore, to try and settle their dispute, but had requested that Malik not be present at the meeting.
On Aug 1, the SNOC's selection committee rejected SA's nomination of Soh for the SEA Games, with the former noting that "since the 2017 SEA Games, there have been numerous instances where Soh has displayed conduct that falls short of the standards of attitude and behaviour that the SNOC expects of and holds its athletes to".
While those instances were not cited, the SNOC and Soh have clashed several times in recent years. Ahead of the 2017 Games in Kuala Lumpur, Soh was formally warned over a breach of regulations regarding his promotion of his personal sponsors on social media.
He had also cut holes in his race vest during the men's marathon final in Malaysia for ventilation, an act that reportedly upset SA's sponsor 2XU.
He is also involved in a long-running spat with Ashley Liew over his teammate's act of sportsmanship at the 2015 SEA Games and the matter is now before the courts.
Low Lin Fhoong