Can I collect my Non-Immigration O visa before the 30 days after applying for extension at Chiang Mai Immigration?

At most offices for 30 day under consideration stamps based on marriage you have to come back on the date they stamped into your passport. I saw one person who showed up 3 days after that stamp expired and they had to start the whole year extension process all over again (AND they were fined 3 days overstay too 😮) Granted that is the extreme but it can happen.

All you can do is GO talk to the immigration office you used and see what they say, I mean face it the worst thing they can say is you show up on that date or you start all over again with the extension process

I asked them that last month. Can only get it on the date.

You applied for an Extension of Stay, not a visa. You can visit the Immigration office earlier but doubt that the checks on documents are ready on earlier date.

You can apply for a re-entry permit but in that case you have to be back before the mentioned date in the under consideration stamp. Discuss this with your Immigration Office.

Usually, you need to return to the immigration office on a specific date. The only possibility MIGHT be talking with the immigration office with the proof of you have to leave...

You are to return on the exact day instructed by your Thai immigration office.