You can get Laos VOA at any Laos land border. I think I paid US$30 last time I went over, which is a couple of years ago, as I had some US cash on hand. I think paying in US actually works out cheaper. You can apply online for an eVisa
The "trailing spouse" visa for non-o is just about extinct now. The simplest way around it is for the applicant to get OA visa and the spouse can attach to this, or for the spouse to get DTV in the interim until attaining 50 years of age
I think you need to brush up on your knowledge. Whatever makes you think credit card purchases do not represent remittances? You are still bringing in money from overseas to pay for goods or services.
I can't understand expats being worried about tax in Thailand. Many, especially retirees will pay nothing. Those bringing in untaxed money will almost certainly have to....and why not?