, with all due respect I do not believe if you report to Chaengwattana (Bangkok) you need to update your TM 6 at the Immigration office. I go to the USA every year and return and do the 90 day report online and update my TM 6 number online doing the report. I have never had a problem doing it that way. I report to Chaengwattana also, as Melanie does.
Your re-entry permit is only good until your current extension expires. So you need to get your extension first then your re-entry. The date you will use would be the date that your new extension of stay expires.
Actually when I had my stamps transferred at Chaengwattana I had the letter from the US Embassy but they didn't even ask for it. That was almost two years ago now though.
Yes, that is correct. She should do the stamps/pemit transfer in a timely manner although there is no written timeline. The transfer service is free. When you get a new passport in Thailand at least from the US Embassy they will give you a letter to give Immigration when having the stamps/permits transferred, I doubt she would get that letter in Laos, but I don't think it will be a problem.
Everyone that receives a queue will get served on that day, it may be late but you will get served. The window I went to was the same as where you get a re-entry permit area. I thought they would call my name but after waiting a long time I went back up and asked and it had been sitting there waiting for me to pick it up.
I would say it depends on where you are located. It gets approved by the office you report to in your area. In Bangkok where I do mine online, the last time it took about 7 hours, it has taken a couple of days in the past also. You can go back to the site and put in the confirmation number you received or your passport information and check the status also, either pending, approved or not approved. It is also kind of a hit or miss it seems to whether you receive a approval email from my office in Bangkok. I did get an approval email the last time I did it, but I think that was a first for me and I have done it online maybe 7 or 8 times now online. So my answer to you is probably 6 hours to a couple of days if your office is utilizing the online reporting. Good luck.