they are managed in a coordinated manner. If the government need to change its immigration policy it will instruct MFA to adjust its policies and procedures to be inline with the new policy. For example if the new Thai immigration policy state that you can only obtain a "retirement" visa n your home country then MFA will stop issuing non imm o visas based on being over 50 years in countries like Laos for non citizens.
correct, but the OP's original post missed the denial of entry and she also didnt say if she's applying for a visa in Laos or trying to enter on visa exempt. I assumed visa exempt.
You are allowed 2 land crossings per year. But you can be asked to show B 20k, flight out and accomodation. Worst that can happen is that you must walk back to Laos at the border.
The non imm b seems simple but its not you need stacks of paperwork every year and you need an wp also (more paperwork). There also has been a clamp down on company owners to make certain the 4 Thai employees (minimum per wp) are real employees. The BOI initially maybe more complex but after that you will have less paperwork each year. For certain investments there are tax breaks etc. Have good look at both and take the route thats to your liking.
Depends on your nationality. Some countries cant obtain visas in Vietnam and Malaysia. Stating your nationality makes giving advice easier for members.