yep you got me, I'm paid by big onward ticket... Do people not have phones, check in desk goes your tickets fake, okay I'll just buy a cheap ticket to Cambodia right now for $40.
People stress way to much about a problem that can be fixed in 5mins with a credit card and a phone.
They can come in visa exempt and extend, but it depends on their airline if they will let them board. Some airlines will want proof of onward travel within the visa exempt period, whilst others don't check at all. You can book an onward ticket for $10-15 online to get around this.
yeah people don't realise how relaxed Thailand's overstay laws are compared to other countries. Generally immigration don't care about a short overstay, but police certainly do. It shouldn't affect you being allowed back in the future and is only 500B per day you overstay. If arrested though the penalty is much greater and you cop a 5yr ban. It's up to you if you want to take the risk, most likely place to have an interaction with cops is being pulled over at a traffic stop.
because this is Thailand, laws only apply if you don't have money. Overstay fine is waived if immigration is closed or if you leave only 1 day over via an airport, so there clearly are exceptions which is what the question was asking.
Just grab a taxi from level 1. It'll only be about 300-400B. Train is useful if it's really busy and during peak hour, but you'll either need to change trains or catch a taxi to your hotel, so I prefer just taking the taxi straight from the airport.