Currently I have a one year multiple entry non immigrant O visa. I need to do a border run for 90 days. I want to leave the country go to Langkawi and turn it in a mini vacation. Will I need to get a reentry permit before I go? If I just do a border bounce to Sadeo walk over turn around and come back, no reentry permit required.

No need for a re-entry permit until your visa expires and then only if you want to leave during the last 90 day entry from it.

Same if the entry is done by land, sea or air.

Dont forget can get a 60 day visit Thai Wife extension from immigration TM7 form 1,900 baht, for every 90 day entry, if you want to cut down on border bounces.