Should I discontinue red LED light therapy after a pdo thread lift?

IMHO, it would not affect your thread lift result to any significant degree. PDO threads disintegrate more rapidly in environments with a lower pH (more acidic) and intense heat. Inflammation reduces tissue pH and thus could hasten the breakdown of the PDO threads. Intense heat (such as laser lipo next to the thread after placement) would also hasten the breakdown. The heat that is induced by a daily at home LED system is very low and doesn’t create significant  inflammation. Thus, I don’t believe this treatment would reduce the integrity of your PDO threads.  However, in my experience best practice guidelines for post op PDO threads is use of COLD compresses for the first 1-2 weeks to help reduce  inflammation caused by thread insertion and allow the threads to settle into place.
This being said, it is best to confirm with your own cosmetic surgeon any treatments that you plan on having around the time of your thread lift.
Hope this helps!