What is the best way to stay in Thailand for 4-6 months as a UK citizen?

To stay 4-6 months in Thailand from the UK, you can consider a visa-exempt entry which grants a total of 90 days without a visa, or apply for a single or multiple entry visa. A border run can extend your stay: with a single entry visa, you could stay for a total of 5 months, while a multiple entry visa could extend your stay to 9 months, requiring a border exit every 90 days. It's also necessary to apply for any extensions, as they are not automatically granted. Considerations for the border runs include how long to stay abroad. There is conflicting advice regarding required overnight stays in a neighboring country for border runs.