if you wanted to take the gf to the uk for a couple of weeks, a tourist visa is what you need. I understand the required salary is going up from 18k to 28k.
The usual evidence, phone chats, photos, evidence that’s she’ll return, such as land, kids, a job.
They basically need to see you can support her and she’ll return to thailand.
good luck mate. I’d applied for the tourist visa, no issues, but as we know, it’s only £18k needed to to meet the criteria. The visa you’re applying for different.
I’m sure more experienced lads can give better advice.