Is my visa plan for staying 9 months in Thailand correct?

Hi everyone, and I have to say this page is an absolute blessing! This is my first post and I have made sure to read a lot on here for the last few months to gain some knowledge however sometimes it's better for me to explain my personal plan and journey and see if there is anything I might have missed, I'd like to also apologise for the first chapter of a story haha so here goes,

I am arriving in BKK on 13th May this is my first time in the land of smiles and I'm so excited! My situation is most condos for long term want 12 months contact for best price which I don't mind doing even if I only can stay for 9 months I'd pay the additional 3 months even if back in the UK I'm currently going through my Tourist visa single entry application and I don't see how I'd have any problems however this is my plan.

(I want to stay around Rama 9 BKK)

Apply for Tourist single entry 60 days, extend for the additional 30 days once in BKK

Going in air to a near by country and returning after the 90 days have expired giving me another 30 days and extending for 30 more days, after this I would do a border run from Ubon to Laos for 30 days + extention 30 days and the repeat this process at ubon for a second time giving me 9 months in Thailand, can anyone confirm if this is logically correct? I know that it's decided at immigration per individual but does my message stand correct if all runs smoothly?

Secondly I'd like to know if it is possible to do the above but then go to Cambodia, Vietnam or Laos after the 9 months end and then repeat the process the following year since it's a fresh year (alternatively I would go back to the UK for 3 months and repeat the process) are chances good for this for me?

Please also note this is my first time traveling from the UK so I'm sorry if I'm a little in accurate and hope for positive feedback, I'm also hoping the lack of travel in me/ my passport will help with doing this for the next 2 years.

I'm 34 and starting to realize my youth is gradually going and I did nothing in those times and life's to short to be bitter with regret and to just do things slightly delayed in life.

Another note as I'm sure you would recommend a multi tourist visa with the length I'm attempting, this is not possible with the evidence required to apply for this as I'm sure the financial bank balance is a massive difference that is required to be shown.

Thank you for taking the time to read this and I cannot wait to hear your thoughts.

Best regards

Luke