Ong'eri, an ally of President Uhuru Kenyatta has reportedly paid ODM life membership and party nomination fee through a proxy amounting to Sh270,000.
Recently, the veteran politician made a surprise move by supporting re-election of Kisii Governor James Ongwae, whom he vehemently opposed in 2013 elctions.
The former Education Minister will vie for Senatorial seat and is expected to face Jubilee's Charles Nyachae and PDP's Omingo Magara who he narrowly beat in 2013, in which they both lost to Chris Obure.
He is expected to announce his move to the Orange party on Monday next week.
Ong'eri was left out of President Uhuru Kenyatta's campaign team in Kisii region.