Ouma, who is also a reserve wicketkeeper, replaces Timothy Mwange, one of two youngsters expected to make their international debut in Canada but neither featured in the Intercontinental Cup nor the two one-day matches Kenya played in Toronto.
The change is part of head coach Roger Harper's desire to improve the run rate from his top order, which has disappointedly failed to deliver in the last four international competitions.
Struggling veteran opener and wicketkeeper Kennedy Otieno Obuya has retained his place despite heavy criticism for his poor batting during the disastrous tour of Bangladesh, where Kenya suffered a 4-0 series defeat earlier this year.
Harper said Kenya, which has won seven of the 11 matches they have played with Test-playing Bangladesh since 1997, would be looking to avenge the defeat.
"This is a new series and both teams start from scratch," said Harper. "In Bangladesh they had the advantage of home conditions.
"We expect to be able to perform a lot better in home conditions and we're looking forward to being very competitive and really trying to turn the tables on the Bangladeshis this time," he added.