Thats sort of it.. But mixing up your visa issues with the bikes visa issues kind of complicates it.. Also as with so much in Thailand local rules may not be the same..
You can bring a bike in temp import, without leaving a cash bond (you give a personal bond / assurance.. So technically liable for a big tax number signed on the form) for 'up to' 6 months.. Depending on the border they will give you 1 month, 2 months (sadao used to if you had a visa, no idea currently) or up to your permission to stay (as they have just reduced land border visa exempt entries to 15 days so maybe that would be used ??) entry time on the bike.
This entry time can be extended at your local customs office... My experiences are its done in 60 day (or 2 months cant remember) chunks.. Failure to do this has a max 2000b fine (so some just ignore it up north) but a bike on overstay is the same as a person on overstay, potential problems if in an accident or other problem. As long as you go to the border in less than 6 months you can pay your fine on exit. Some places are super easy going, others are not, all about local enforcement.
If the bike is in bits or having major work done, you can get another month or so after the 6 months.. But thats really pushing it and is a one off. It was allowed one time on a mates bike that was being repaired and he knew the customs guy well.. He ought to as he saw him every 2 months for years regularly extending his USA regged Harley.