I'm actually considering the marriage visa. Simply cuz I don't believe in marriage and it makes everything really easy so I've heard after when it comes to long term stay in Thailand. Just don't mention anything to your home country about it so it's only 'official' in Thailand. I wonder how many here have done it already... finding a Thai woman is the easy part, I just wonder how to make sure you are still a single guy outside of the thai borders so you don't have to explain one day to your actual future wife (if ever and assuming she won't be thai).

Just make sure you don't get paid from a company registered within thai borders. Remote work is fine on any visa.

There's never a letter O in a passport number. This is to avoid confusion. And while I believe it's just stupid you didn't check this beforehand by a simple Google search, it's even more absurd that they refused it because of this. They know right away what's meant when a letter O appears.

Just go for a local sim.

If you have a little money to spend you can pay ~1600 baht for unlimited data 1y (order in shopee).

When you leave after a month, give it to someone who struggles to pay the rent.

#makesomeonesdayforjust1k