6 months is easy if they don’t change the rules fly in on visa exemption get 60 days extend 30 days locally for 1900 baht. Do one border bounce with agent giving another 60 which you can extend for 30. Total of 6 months, this can be repeated again giving another 3 months.
The 30 day extension is nothing to worry about if your relaxed. I’d recommend doing it in the last 2 weeks of your 60 days. The only thing you need to make sure of is your accommodation before you go to immigration has registered you. This is called a TM30. Best to take a print out of this. It’s not required on Koh samui but was required in Chiang mai.
do your own research but my friend booked a 2 day cooking course and got the DTV visa. 3000 baht for the course and you can stay in Thailand for 5 years.