BBC | Several accused him of "re-traumatising" Grande. The pop star turned actress has spoken of experiencing post-traumatic stress disorder after a suicide bomb attack at her May 2017 concert in Manchester, killing 22 people and injuring hundreds.
In Wen's trial on Monday, the court heard he had attempted to intrude on the movie premiere twice, Singaporean media reports.
Moments after he grabbed Grande, her co-star Cynthia Erivo forcibly pried him off and security staff escorted him out.
He then made a second attempt to jump the barricades. Security staff stopped him and this time pinned him down.
Wen later posted videos of the incident on his social media accounts thanking Grande and stating that he was "free".
Police in Singapore arrested him the next day and charged him with public nuisance. Wen pleaded guilty.
Prosecutors sought a week's jail for Wen, arguing that he was a "serial intruder" who publicised his behaviour to gain popularity online.
Wen has posted videos of himself disrupting concerts by Katy Perry and The Weekend, and invading the pitch at various sporting events. Australian media have reported he is banned from some stadiums and has incurred large fines.
Wen, who was not represented in the Singapore court, told the judge in mitigation that he would "not do it again".
Under Singapore's laws against public nuisance, Wen could have been jailed for up to three months, fined up to S$2,000 (£1,167; $1,537), or both.
Grande has not commented on the case, while continuing to appear in public at events in Los Angeles over the weekend.
But two days after the incident, Erivo appeared to allude to it when she spoke about her relationship with Grande while making the movie, saying: "We have come through some stuff in our lives, our daily workings... even this last week, let's be honest."