Thanks for that link. I think, looking on to the next section, that that is likely to be interpreted as if, if one shared hotel at a time on holiday(s) was all there was, it wouldn't count, whereas a bit of hotel time added on consecutively with a more solid formal arrangement it could, as with the other people's hotel + plane ticket + another hotel in another country + another plane ticket and so on with extra evidence of shared life, when it was obvious from the extent and timing that this wasn't just a holiday relationship.
You're quite right that INZ did offer another couple a partner-sponsored visitor's visa instead of the partner-sponsored temporary work visa they had applied for. The evidence of partnershp required for both is the same. Evidently the CO was convinced it was a partnership, but didn't have quite enough boxes ticked for issuing the partner-sponsored temporary work visa straight away, so gave them the chance of putting in the extra time (and therefore, evidence). So evidently, INZ
can do this, but there's no way to tell from outside in what exact circumstances they will decide to.
As to leaving after you've sent in the application, of course you'd have to do that if your Thai visa was about to run out, to keep legal. In one way that shows up as evidence for your good character, but not being together never helps. Therefore, you need to have as much and as solid evidence as possible on all other angles of maintaining the relationship - for instance, if you each have bought things that will be for your future shared life, and the purchases show up on your financial details as well as being mentioned in emails, photos and whatever.
I wish I could help your peace of mind by saying that THIS or THAT will work, which I can't, not being able to read the future. But I wish you all the best, with crossed fingers. +++++++++++++