Either method should work just fine. I tend to thin to one plant per pot. Today I'm starting some French Thyme cuttings and will go to 4 cuttings per small pot.

Personally, I have never had much luck establishing thyme from seed. I can get it to sprout, just not establish into a thriving plant once outside. Five years ago, I bought a common thyme plant from a nursery for $1. What started out as a little plant in a 2" pot is now so established, I have to really keep on top of it else it would take over the spot it is in (in Zone 5 in MI). One thing about common thyme, it roots easily from the stems. If you have a plant that is scrawny, bend over one of two stems and cover with soil (making sure the end of the stem is exposed to light). The part of the stem covered with soil will root and send up many new shoots.

Unless seeds are either very expensive per seed or quite large, I sow more than one seed in a "pot" for any seeds I'm starting. You can always prick out the seedlings or thin later on if you have great germination.

I tend to have limited indoor starting space and so some things I just try by direct sowing. I was given some thyme seed a number of years ago and so I just direct sowed it into my vegetable bed. I had pretty good germination. I ended up with 4-5 young thyme plants out of it.

FataMorgana