I applaud your responsible attitude but honestly, you’re way over thinking it. You are not going to be even slightly on their radar but if you have the funds to waste and do it all legit, then up to you as they say. Good luck with whatever you’re doing.
Assuming you are going for more than 45 days, do yourself a favour and get a 60 day TV. It will negate any potential problems with the airline on way out. Also, it’s just wasted time and hassle at immigration office when extending your stay. The cost of the TV and extension are comparable, so no real advantage in not getting a TV.
Because you’ve read it wrong. He’s currently on his extension now, but thinking about what happens in 3 weeks time when it ends and he still has 6 days left in Thailand.