Clearly you don't know anything, otherwise, you'd know very well that Kip are accepted for the visa AND can easily be purchased from one of the money changers at the border on the LAO side in Vientiane.
I have crossed there MANY, MANY times over many years and also at other borders. There are zero issues paying in USD over Baht or vice versa. Notes must be in great condition, that's all.
Yes although money changers are much better. They're everywhere now...not just in Bangkok or tourist places like Pattaya and Phuket. Most larger towns and cities have money changers, from Mae Sot to Lampang, Nakorn Ratchasima to Khon Kaen, Udon Thani to Nong Khai, Ubon Ratchathani to Surat Thani and so forth.
Nonsense. Nong Khai is the Thai side, Thanaleng or Vientiane is the name for the Lao side. Get it right or people will be confused.
No one has ever demanded payment in one currency over the other. You ALWAYS had a choice.
Also, there are MONEY CHANGERS on the Lao side. You can purchase Lao Kip right there. Duh!!
Not to mention there are money changers stocking Lao Kip in Thailand. Might not be easy to find (except in border cities) but money changers are definitely able to purchase Kip and sell some, if in stock.
It is in my opinion. Considering the proliferation of money changers in Thailand, it's easy enough to get some foreign cash (in this case USD) without putting much effort into it. Of course if you apply for a Lao evisa (which is more expensive than the Lao visa on arrival) you probably won't need to bother exchanging any money at all.
That's exactly what I meant! Thailand isn't interested in what Lao imposes or what currency they prefer. Incidentally, you CAN pay for your Lao visa with Kip. They'll charge you more than in USD but less than if you pay with Baht.