You really don't need another TM30 filed unless you want to do some business at immigration. If you have a primary residence then file there despite where you travel around to within Thailand
In the end it's easier to border bounce. Extending is a real hassle you have to go to immigration you have to provide all the updated paperwork from your initial application plus you have to show the $500,000 in a bank for a minimum of 30 days then you have to wait a 2 week under consideration period while they send the paperwork to the main office.
You can't have any business interactions with Thai entities, clients, etc. the business needs to be registered outside of Thailand. Although there is no income requirements you'll need to show a viable real business with contracts and clients or a history as a freelancer.
You'll need the bill of sale, copy of their Thai ID and house book, you'll need the transfer papers completed, you'll need possibly two power of attorneys signed by them so that you can change the bike plates and register your name in the green book to your province