@Caleb *******
You (although technically it's her application) apply online and then submit everything at VFS in Bangkok. Now they scan everything to the UK where the decision is made. Settlement visas are no longer decided by the Embassy in Bangkok (although Visitor visas still are).
You will need to exactly meet the financial requirements as described by Gareth Youaintseenmeright Davies, and prove you are in a sustained relationship. She will need to pass the A1 English test (this can be done in Bangkok) and have a TB test. You will also need to show that she will have accommodation in the UK.
If she gets the visa she will be able to work in the UK. In 30 months she can complete the next stage on the way to Indefinite Leave to Remain and then, eventually, citizenship if she wants this.