Do not read your DM, your friend does not need an agent. Your friend can enter Laos today and get 30 days visa exempt. Mukdahan border is hassle free border, they do not ask for anything nor question you. Your friend should have done that right away since he's only gonna be in Thailand for 7-10 days. p.s: As said above, Savannakhet has had a 2 consecutive tourist visa rules for a long time. And also if you have history of volunteer visa you cannot get tourist visa there anymore.
Then why is he doing a tourist visa if he's only going to be in Thailand for 7-10 days? He should have in and out Laos in 30 min hassle free. He can still leave Laos today hassle free and get 30 days.
p.s: Savannakhet only issue 2 consecutives tourist visa, not 3 or more, thats why he got denied. p.s.2: Mukdahan is hassle free border. Wont be ask anything.
Suvarnabhumi is notorious to work hand in hand with agent. There is a 6-8k baht bribe there to get into VIP line for people with suspicious passport (history of ed visa, volunteer, or simply a lot of stamps). So officers there will be tough to indirectly encourage people to use agent. Also, this is Thailand, they do not need a plausible reason to deny you entry. It's up to them if they allow you in or not without a bribe.
That's not how it work. Visa obtained via bribery have the same stamp as the one without the use of agent. Officers at Suvarnabhumi have no way to know if you did it under the table or not. So by default they will be tough on everyone with history of Ed or/and Volunteer visa at that specific airport. For a multitude of reason one of which their connection with visa agent (bribery, 6-8k bribe to use VIP line).
That there is no distinction if your ed or volunteer visa was done properly or not. Which mean whether or not you went to school, or actually volunteered, change nothing, you wont get the elite visa even if you are now fluent in Thai due to the ed visa.
Rookie mistake! NEVER enter from Suvarnabhumi Airport if you have a history of using Ed or Volunteer visa, even if done without using agent. The chance of getting denied entry is very high. But, you can use an agent to get VIP line at airport for 6-8k baht which will ensure that you get in (it's common bribery at Suvarnabhumi airport and one of the reason why they denied entry to many people (they want you to use an agent). You cannot get elite visa with your history, but you can come back into Thailand anytime you want if you use agent at Suvarnabhumi or if you enter by land.
OP is talking about border run, only 3 or 4 border are "fierce" in Thailand, one of which is Poipet. Most borders are hassle free. Just like by air BKK are fierce, and lately Phuket, but most airport aren't. A lot of people spread misinformation with no nuance and it end up being detrimental to people who are looking for solutions.