It was a BS thing, I had 2 friends ride 1150cc BMW'S to China, they weren't allowed to cross in because they were over 200cc, soon fixed by putting a 198cc sticker over the 1150 sticker.
local insurance was only about 500 Baht for 21 Days. It is pre covid I did this so it may have changed. You need a simple carnet to bring the bike out and in. You use to be able to do at the border. 5 years ago so you need to check.
You can go easily to Malaysia, Cambodia you can do but last I heard you have to go to a certain check point, and get an agent to arrange. Wouldn't even try Mynamar. Vietnam you can but there used to be some funny regulations about engine size, I think had to be less than 200cc.
I go in 8 or more times a year by plane, never overstay only once the past 20 years have they asked to see my return ticket. I've stayed from 4 days to 30 days but not more than 180 days in a year.