Yeah, should be enough time. Kratom won't block oxycodone afaik, it does contain opioid antagonists but these are of low affinity and potency. I even got effects when taking an opiate plus Kratom together.
Yeah it kind of potentiates it in a way so I wouldn't trip..if you are worried about ODing and harm reduction then yes just wait a few hours but all in all they are fine to take together