Out of curiosity, if the answer is known, were they denying arrivals with Non-Immigrant O and B visas, or was it primarily Tourist and Visa-Exempt arrivals that they were turning away?
I would say an overstay fine is for sure, as the date in the Under Consideration stamp is the date until which you permitted to stay in The Kingdom. Whether or not you'll be allowed to re-apply, or be granted the additional 45 days once you have paid the overstay fine will be up to the officer handling your case.
It says, in case you're not a citizen of the country in which you're applying, but you are a citizen, so your passport should satisfy that requirement.
Lao, Cambodians, and Myanmar nationals have 2 different passports they can get. One allows them to work, the other allows them to visit only. There are also 2 different working passports (for people from Myanmar at any rate, but I assume the same is true for Laos and Cambodia from what I've seen my friends do). One is obtainable from their embassy in Bangkok, the other has to be obtained in their home country, but is "better". I'm not sure exactly what is better about it. Perhaps longer permitted stays. It takes about a month for them to process that one.
When I was in Vientiane in May there was a Chinese national applying for a new B visa. The embassy denied her application and told her she had to go to China to get one. She was given a visa-exempt entry at the border and was next going to prepare to fly to China.
It was about 10 a.m. When I got there. I'm surprised to see people say they never had to sign in, because I always had to, which included writing down your passport number.
To clarify further, this was at the door where the shuttle bus drops you off. I didn't think to check the other entrance to see if it was the same.
More to the point, government offices will be closed. Chaengwattana Road is not an artery to Rattanakosin, and as most people will not be working it's possible that traffic in Laksi might actually be lighter than usual, but that's an assumption on my part. It may become jammed with traffic from people coming from provinces Northwest of Bangkok.