You choose the embassy based on where you are PHYSICALLY.
If you're in Laos, then you can use Vientiane if you're in the area that the Vientiane embassy covers, or you use Savannakhet if you're in the area that the consulate covers.
Same for Vietnam, when you're inside Vietnam you choose the embassy that covers where you are in Vietnam. They each cover different sections of the country, and it's best to keep to it because they can reject your application if your proof of location doesn't show that you're in the right location.
Also they can call you into the embassy for an interview so best to choose the one that's closest which should be the one covering where you are physically.
Something to keep in mind about Laos, the embassy and consulate there are the only ones that require you to go in person and pay after you submit your application online. That's not required in Vietnam or anywhere else except Myanmar.
As an example, here's the map of embassy and consulate coverage for the US.
the officers at the immigration office have nothing to do with the ones at the airport. Whatever they tell you is irrelevant. It's 100% up to the person you are standing in front of. And the law says cash only for tourists, not bank books.
Anonymous participant 746 then you didn't get any extension. You were denied an extension and received a stamp that said "extension denied" along with 7 days to vacate Thailand
You can enter visa exempt as many times as they let you. If you get an extension, the first one is 30 days. If you try to get another extension in the same year, whether on your 2nd or your 5th visa exempt entry, it will only be 7 days. That's how it's currently working. But as all things, it's up to the discretion of the immigration officer.
Anonymous participant You're wrong in that they don't give you any time to leave if your work extension ends. Your permission to stay in Thailand is invalid as of the day your work ends.
Only if you are employed with a BOI company do you get a grace period.
It's only popular because of a headline. The chances of actually being asked are very, very low. You should know if you are at risk because you have been abusing tourist entries trying to stay in Thailand longer than a tourist should.
IF you get asked to show proof of funds, it must be IN CASH ONLY. They will not accept credit cards, debit cards, bank statements, banking apps, or anything that is not cash. The only reason they ask this question is if they already want to deny you entry. So they are not going to bend over backwards to let you meet the requirement when the law specifically says cash only.