Can I re-enter Thailand using the visa exemption scheme after a 30-day stay in December?

No worries.

Two suggestions:

1) when you’re checking in for your flight in the UK, the airline may check to make sure you have an outbound ticket from Thailand 30 days later, since you won’t be using a visa. So, if you already know where you’re going to after/between Thailand flights, have that ticket confirmation easy to find on your phone. (Or print it out so you can just hand the check-in counter a copy.)

2) If you’re going to be flying in and out of Bangkok, check out LEO Self Storage. Their Chinatown location is near a lot of great cafes and restaurants, and also just a few minutes walk from the train station. LEO offers bag and locker/room storage, but they also have really inexpensive container boxes, about $5 a month, that are about the size of a checked bag, which they store in racks in an air conditioned room. That can wind up being much less expensive (and less stressful) than checking a bag on a round trip flight, and it’s also a great way to free up space in the luggage you *are* carrying, to make room for souvenirs and gifts to take home. Personally, I’m gradually building a box of stuff I can just leave in Thailand year-round instead of carrying it all back and forth on planes. And that makes it feel even more like I’m just coming home when I return to Bangkok. (The staff at LEO is also really nice, and they have some awesome local food advice.)

Yes

Have fun 😁

One word Yes..

Yes

Yes technically you should be fine

You shouldn't have any issues with your plan