Continuing the discussion from A! Donc, an- o tuma, an ma bɛn! Ne ye Jalo le ye dun!:
Yes, O tuma and O tuma na are both correct and possible!
(“O tuma” followed by an apostrophe occurs over 2,000 times in the Bambara Reference Corpus. And “O tuma na” occurs over 1,000 times. There’s even “O tuma la” over 300 times.)
The postposition la/na is optional in a number of special cases often related to time, place or manner (and relative sentences). For instance:
O don (na), n taara
‘(On) that day, I left’
Or in relative constructions:
Christy sera Bamakɔ don min (na), à ye dibisogo san
‘The day (upon) which Christy arrived in Bamako, she bought dibi meat.’
(as in, “When Christy arrived in Bamako, she bought dibi meat”)
Or:
N m’à dɔn, Christy taara yɔrɔ min (na)
“I don’t know the place (to) which Christy went”
(as in, “I don’t know where Christy went”)
This variability also applies to other cases such “O tuma (na)” on its own. Hope that helps!