You can buy bus tickets out of Thailand. You don't have to get on the bus but it will serve as proof of onward travel.
I believe you can get a 7 day emergency to avoid overstay, I am not sure the requirements.
I assume if you are overstay by a couple of days it's no big deal and it will not likely cause you problems in the future. But that is only a guess and you assume the risk.
You could do a border bounce, possibly. Cross over the border, get some lunch, come back.
I have done a lot of questionable stuff to get visas and it usually works out for me. I have always avoid the overstay. My thinking is that I don't want to give immigration a reason to deny me entry.
my clients and bank accounts are in the US. I send money to Thailand once a month. Thailand knows about the money I send to the Thailand but they have no way to know about money that stays in the US. What I am trying to say is they have no way to know if you are freelancing or not. I have never been asked by people who matter if I work in Thailand.
I think Thailand's two larger concerns: A) Are you taking a job from a Thai person and B) are you paying your taxes.
Taxes are a lesser concern, but the government has said they'll crack-down on that, some day.
I applied for my 90day marriage visa online (USA). They didn't ask for proof of funds. I don't know if that is a US thing or not. Also, I have been able to apply online while not being in the US. The US embassy seems flexible on the matter regardless of what the eVisa website says. That is the US embassy the I am not sure about Brazilian embassy.
I also work remotely, without any kinda of work permit. Up until recently remote work was kinda of a unheard concept in the Thai government. This group has individuals with opinions and not always do those opinions matter, the immigration office nor embassy, does not consult this group to make decisions. You will find good advice here but not all the advice is good.
If I were in your position, I would look for more remote work instead of trying to find work locally. Unless of course you already have something lined up.
It's possible to get a 1-year marriage visa extension without funds, sometimes. You would go to an agent and they would charge you a few bucks. They would deposit the funds for 5 minutes, you would get a bank statement, you would transfer the funds back to them. That agent would have a friend in immigration (tea money).
The ''she dunno" was the cause of her problems. I have a questionable visa history. Don't listen to these other people in this group, Thailand is very flexible about who they let it. But they do randomly pull people aside and ask for further documentation and it's best to have that documentation.
I do not know. But I would think if they present their ticket to Cambodia when checking into the Thailand flight they would be allowed because they're not going to Thailand.
However, I don't actually know. I think that would be a question for the airline.