You don't get a denied entry stamp. Officer says you're there too often so they send you to the supervisor room. The supervisor write some stuff on a paper with reason of denial (they can't write "too many entries" so they make something up). He also enter you in the computer system. Then I take the bus to the Laos side again, and I show them the paper and they direct me to a room where they will undo my used Laos visa stamp (as if I never left Laos). So no, I don't pay the Laos visa twice.
I did use an agent, but the agent is never the person waiting for you. The agent is in an office somewhere in Thailand. The agent work with immigration officers. An officer will wait for you near an immigration gate in the airport. They have your picture so they know what you look like. Then you follow the agent through the priority lane to her booth. She's the one who give you the 60 days stamps. So basically the agent work directly with one or more of the immigration officers who stamp your passport at BKK airport.
I would guest that every single officer who work in priority/business line at airport work with one or more agent to make extra money. It's easy extra money for them. And no, you don't need onward travel, that's the biggest myth ever.
I went through a standard priority lane, people there didn't look old nor disabled. I think business class can go through this line. But I skipped the priority lane straight through the booth with officer who greeted me at the entrance. She opened her booth just for me. I just skipped through ahead of people as you do if you are able to miss your flight, for example.
No, both extensions are NOT in the same calendar year. No, both extensions are NOT counting consecutively and does NOT start counting per your February extension. Each entry is UNIQUE and treated individually. There is no such thing as a February extension if you leave in April. Your new entry in 2025 will exclude February, so your entry calendar year will be from April 2025 to December 2025. 1 extension PER entry. Because the calendar year exclude previous entry and start counting the day you enter until December 31.
The counting start the Day you enter the country. You don't seem to have any knowledge about how the DTV work, or how extensions are calculated. Day 1 is your entry, which may or may not go to 365 days (extension at 180 days). It depend on you if you want to stay the full amount or do a quick border run and re-enter. What you can't do is extend in February and let's say August, without leaving the country.
You are failing to understand that your November 2025 would be your FIRST eXtension of the year, not your 2nd. The second that you leave (April 2025), the year END in relation to your entry and past extension. it reset April 2025 upon coming back. Or, to make it simpler, ONE extension PER entry.
There is no such thing as 2 extensions in 1 year. You are confusing border run with extension. You said, and I quote "leave april 2025". the second that you leave, you come back on a NEW entry, therefore you are at 0 extension for that year (for that entry).