I am one of those..last year. Just ensure you have proof of a ticket out before visa exempt expires..do the extension ..then initiate actual visa by border crossing/return bearing in mind you submit actual visa # and paper copy which was emailed upon award from Thai Embassy.
exactly my situation last fall..received my delayed evisa on the very day my (then) 45 day visa exempt expired. Entered Laos then to initiate it, and critical to have onward flight booked to satisfy departure within limits of the visa exempt period..it is totally the airline's scrutiny, admission for visa exempt went without a hitch...(Canadian PP and departure point)
If you do use Air Canada that is a definite..book an onward ticket just before expiry to satisfy departure...(online temp reservations can be found by google search for exactly that.."onward travel". Suggest you avoid online pre checkin since, at least in AC's case..they will request a visa and there is no provision to input anything like a visa exempt status ..and raises flags. However, with an onward ticket reservation and your flight locator # you should be fine..and when you arrive in Bangkok you should sail through with 30 day visa exempt but wise to have a hotel reservation to satisfy TM30 requirements...something you will find out about should you apply for an extension in country later.
It took me about 3 months to get 6 month multi entry visa since new post covid e system was established..(additional info on several issues was requested, mainly financial). I had six visas prior to that which involved just sending passport in to local Canadian center and getting it back within two weeks..As a result, flight time came and I entered under visa exempt, only to finally receive the multi entry about 3 weeks after arrival..I kept local Immigration notified, and initiated multi entry at a Laos crossing. Remember the only proof you have is the attachment sent by email when visa is finally approved and you need that each time you do your 60 day bounce, since all that appears in your passport is regular entry stamp , not full page "plate" type used in the past.
I have done 2 crossings @ Mukdahan this year (to update a multi entry visa). Although, I had brought both currencies..they seem to prefer Thai Baht..and yes, traditionally new crisp US dollar used to be preferred..in contrast to what I used in Nong Khai a few years back.
if you want to chance it..download the form and do as much of it as you can yourself..pull it out if asked..and , at least they will know you have tried..suggest you just play innocent , and only briefly describe the difficulty, and sort of indicate that is not intended to get the landlord in trouble..go gently.
thanx....and will post if there are any changes re Chiang Khong (for my situation , at least). I've only heard about the the COVID stuff (np in my case)..AND the need to get transit papers before Thai exit (ones Thais get to cross) , and for non thais ..supposedly a charge .....used to be my normal exit bounce pre COVID so I think I shall stick with Chiang Khong/Huaixai , since it went smoothly 2 months ago.
Good suggestion...but having done the Chiang Khong trip last time, and rather like the trip itself (live in Chiang Rai, and hire a car) ..going up one way and come down another (following the River Kok, with many great riverside stops to eat) ..last trip was on a Sunday, and at least that particular time , afforded a very fast and friendly border experience...