My renewal of non-imm. "o" visa extension of stay is due at a time when I plan to be traveling in Europe and U.S. Can I get a new extension of stay prior to leaving Thailand even if it is up to 2 months prior to the due date? Appreciate any advice, but I do plan on asking at immigration offfice what their policy is. I'm just curious what other folks experiences are regarding this issue. Thanks.

Norm is that you can apply up to 30 days early. But often allowed to do it earlier if there is a valid need to do it early, such as need to travel.

I hope it is not an extension of stay based on marriage, that is more problematic.

I needed to do a renewal of my marriage extension in Nonthaburi, am due to fly out of Thailand in early December, so went 4 days earlier than the 30 day requirement, as I was worried I would not receive my extension in time, the female officer (who is very kind) looked at the documents, stamped them all up and returned them to me asking if I could come again on the 31st October, as that was within the 30 days, went back saw her again, no problems documents taken and promised that the 30 days would be 30 days and not more, as this might affect my travel plans.