I have non imm want to change to 1 year retirement wich I have had in the past. Have still x2 months to run on my non imm. But I need to leave Thailand on 28 April will not be back until 5 July my non imm vsa will run out. CAN I change to 1 Year Retirement Visa NOW before I leave Thailand. I have all the requirements.

You can change your reason of stay to reteirement without any problem. Normaly immigration will do it in the last 30 days of your permission to stay, but in case of a good reason they will often do it earlier. If not, you will have to apply for a new non-O visa abroad and an extension of stay later.

I suspect you will have to obtain a new visa and then wait 60 days after you return but you can ask. They sometimes will do early but this is normally a person who already has an extension of stay.