What are the chances of my Thai wife obtaining a 10-year multiple entry visa to the UK after successfully receiving a 6-month tourist visa?

If people aren't lawyers, I would take any advice they give with a pinch of salt (a bit like the earlier poster who said that 10 year visas weren't possible simply because they had never heard of it). Very few understand the actual requirements, and whilst many do get visas without extensive documentation, this will make the process into more of a lottery than it need be. If you are familiar with the old military phrase PPPPPP then it is well adhered to

It isn't a particularly difficult process but it does need some planning and some time expended on it in order to ensure the best chance of success

Any Thai documentation provided such as Blue House Book Baan, Chanote, Vehicle Blue Book etc. should be translated into English. Don't provide documentation and expect it to be translated by VFS in Thailand. They won't do it, and no translation means that the document is unlikely to be accepted

Unless you are very confident with dealing with the documentation required, I would recommend that you have a lawyer or visa professional assist you with the process. A lot of people are rejected because they fail to provide sufficient documentation etc. You should be prepared to provide a covering letter with quite a lot of detail about your relationship with your wife, her family, your family, your life together and purpose to visit UK, how you/she will be supported during that time, and why she should return to Thailand (previous visits is always a good indicator etc.). Some may argue that this isn't or shouldn't be necessary, but my recommendation would always be for too much rather than too little. Supporting documentation should be as extensive as possible and if possible letters and supporting documentation, photos etc. from family in UK

Long-term visit visas

If you can prove you need to visit the UK regularly over a longer period, you can apply for a visa that lasts 2, 5 or 10 years. You can stay for a maximum of 6 months on each visit.

Well, most businesses do levy a charge for their services or else they can't remain in-business. Whether or not you decide to engage their services or try doing it on your own, is your choice. Good luck Paul!

I was told that it was, but maybe you should send them an email and ask. Sorry, but as an American I can't help you much more than this...or try to google for an agency to help. Good luck Paul!

My missus sat for a week researching thai forums online. And we took a folder an inch thick. Overkill but hey it worked no problem. Same for her 10 year USA multi entry

Obtained ourselves.. but about 7 years ago. I think it was 30k.