Tongan MP Vatau Hui was last week convicted and fined in the Fasi Lower Court after pleading guilty to failing to submit a report of his financial campaign expenses.
Kaniva News reports a local Magistrate fined him a total of $US129.
The court was told an Electoral Commission investigation found Hui failed to report his campaign spending and police were alerted.
Candidates can spend up to a maximum of just over $US4,000 on election advertising and are required to file a financial report after every election.
Hui unseated a former Minister of Internal Affairs, Fe‘ao Vakata, during the 2017 November election.