Non-O won't change anything in BKK airport, they are annoying af with cases like OP. He could land entry from Laos, very easy on visa exempt entry. I think if he was over 90 days they would have said so upon leaving, so he probably got lucky.
90 days+ = ban for 1 year. BUT... it's exactly 90 days so he might get lucky at the airport. BUT... he need to avoid Suvanabhumi airport, as they are ruthless with cases like your husband. I suggest that he fly to Phuket and you meet him there and you try to talk to officer yourself and explain the situation with the kids, etc. You might have to beg... but you have to do what you have to do...
Assist Thai Visa only have 467 FB followers, with 11 FB total reviews. I would strongly suggest you to NOT use an agent with such little following and reviews.
In comparison, Thai Visa Centre has 22k followers, and 1540 reviews.
In fact, if you have the 800k, you DO NOT need to use an agent at all. If you need help, use a lawyer that do not provide agency services.
In brief, it's bribery. The bribery in Phetchaburi is not recognized in BKK, and vice-versa. Went you pay an agent good money to help you, the agent pay IO and more down the chain of command. Only a fraction actually stay in the agent pocket.
Nobody screwed you. Agent are all illegal. But your stamps are legit. Your stamps won't be recognize by BKK because of how you got said stamps elsewhere. Not a single agent could have prevented what happened to you today. The recommendation you got from CW IO today is what everyone does went they want to extend without using an agent they previously used. You need to leave the country like he said and apply again.
First of all, you are NOT on overstay. A lot of awful misinformation going on in the comments. What happened is that you used an agent last time, so you are bound to use the same agent + same immigration this time around too. It's the downside of using an agent, you are stuck with them for future extensions because they way you obtained said Non-O last time was illegally obtain but the stamps are legit. To erase that, you need to leave the country and apply for Non-O in neighbor country. So when you come back in u will be able to extend for a year no problem.
He is not on overstay. But because he used an agent a year ago, he is stuck in using them again with that same immigration. That's the downside of using an agent, unless you leave the country and come back with fresh stamps you have to re-use the agent forever.
Yes and No. First, please understand that EVERY agent are doing things illegally per Thai law went it come to helping you out for whatever visa or extension related, even in your case. Second, some agent are just there to scam you, they can't give you what they promise, but others (like Thai Visa Centre) will 100% provide what they promise you, and your stamp will be legit. Something can be illegal but legit. For example, the black market for lotto ticket is illegal in Thailand, but if you buy a lotto ticket from the black market and win, you will get paid, therefore it is legit. The opposite of legit would be a scam... you give 20k baht to an agent and he run with your money. Selecting an agent that is reputable matter, because the scammy one rarely if ever face consequences for scamming foreigners.
The whole point of using an agent is to get around the financial requirement. The agent will put the money in your account for a few days, or won't even, it depend.