Yes but from what I can see the application for extension takes longer and if you have only a four week window it might not be long enough. I have same problem but being in repair on vessels I never have a regular schedule. I used to get the one year from Loas but that has stopped. I saw Thai visa center can actually do a retirement extension in one week which I may have to do this if I get any hassle coming in on tourist exempt.
I did ask the boss in my local gym in Om Noi after someone else asked similar question. He pays his trainers
*****
a month base plus commision on lessons and most of these trainers have degrees or have been body building champs in Thailand. Hour lessons cost 1500 baht and they never had any foriegners do, but this is out of the way. But they have hell of a lot of people doing personal training
Do tourist till they stop you, then change to retirement visa. Dare i say it probably better doing it with an agency. Thai visa center can get you visa and extension within your time frame. Problem doing extension some places can take more than a month.
You could also get OX or OA visa in australia you would have to check embassies website for more info. The OX is apparently quite easy from Australia