The 43-year-old, who now resides in Malaysia and is unemployed, last week filed a judicial review application against the Immigration and Checkpoints Authority (ICA), claiming a "breach of natural justice" which had "violated" his right to a fair hearing. He added in court papers that the decision was made "arbitrarily and/or unreasonably".
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This latest application was filed a day after he applied for a High Court judicial review of the university's decision to sack him in May last year, according to The Straits Times.
He had already been suspended by NUS in July 2012.
Mr Tey, in court papers filed last week, is claiming there was a breach of natural justice as he was not given a hearing. He is asking the court to quash the university's decision and be reinstated.
He was first charged with corruption in May 2012 over allegations that he accepted gifts and sex from Ms Darrine Ko, a former law student at NUS.