The New Zealand-born 26-year-old was sent off over the incident during a reserve-grade NSW Cup clash against St George Illawarra last week.
He pleaded guilty at a judicial hearing on Wednesday evening.
Kepaoa "issued a personal apology acknowledging the harm caused by his choice of words", the Knights said in a statement.
"Language that causes harm to individuals or communities has no place in our club, in the NRL, or in our community," the club added.
Homophobic slurs in the NRL are rare.
The last player to be charged was the New Zealand Warriors' Marcelo Montoya in 2002. He received a four-match ban.
In contrast, there have been nine similar incidents since the start of 2024 in the AFL, most recently this month when the Gold Coast Sun's Max Knobel was banned for four games.
Kepaoa's punishment came just weeks after former rugby league hard man Kane Evans came out as gay - only the second man from the sport in Australia to do so and the first since 1994.