Affirmation to Marry - Dual Nationality

Hi,

I've got a question regarding obtaining an affirmation to marry being a dual citizen. I currently spend most of my time residing in Thailand on a non-B visa and when I'm not in Thailand (or travelling the region for work) Australia is my home. Australia has also been my home since before I came to Thailand for work. However, my Thai visa is in my Swiss passport (as you can tell I'm a dual national of Australia and Switzerland) but from what I can tell, obtaining an affirmation to marry from the Swiss embassy involves too many steps and may take weeks (or more).

Could I just go to the Aussie authorities and do a stat dec and not worry about the Swiss? I hope the Amphoe only requires a copy of the front page of my passport though. Of course, if they need my visa and entry stamp too that is no problem, but they better not ask anything regarding my lack of documents from the Swiss authorities. I have not lived there in years (not since the 1990s) and in fact, I'm registered with the Swiss authorities as living in Australia.

It would also be very complicated to get a new Thai visa in my Aussie passport just for the purposes of marriage. I could do it once my current visa expires but that isn't until the end of October 2016. The main reason for using my Swiss passport is due to frequent business travel to Laos, which doesn't require a visa for Swiss nationals, but does for Aussies.

Anyone have experience marrying in Thailand as a dual national?