Visa For Old Friend (now Girlfriend)

Hi. This is a bit of a weird situation. I want to bring my new girlfriend over to the UK. I've known her roughly about 5 years, we were almost like best friends before but I was in another relationship at the time. I've been with her in a relationship now for about 4 months.

She has always worked and taken care of herself, she has 2 jobs and earns quite good money (for a thai) between 20,000-30,000 baht per month, but some of it is comission based so there's no set wage. But she has no savings,also she gets payed cash so has no bank details to show how much she earns.

Her English is probably the best i've ever heard a thai speak along with British accent. I do have quite alot of concerns about her obtaining a tourist visa though. Like we always hear about the embassy wanting to see if they have somthing to return to e.g house, car,business etc. She doesn't have savings but she can get letters from both employers saying she has a good job to return to, one of her bosses isn't thai, he's from holland. But the other boss is thai. I'm not sure if it matters or not who the letter comes from? If needed I can get an invite from my family saying she can stay here as they have met her on a previous trip and really liked her.

Also the embassy want photos,proof of relationship etc. We only have pictures from the last 2 months and no phone bills as i've been over in thailand with her.But we are not in any rush to get the visa straight away so would it be better to apply in a few months when we have more proof of a longer relationship?

Thanks to anyone that can help with my questions.