Do UK citizens need a visa to stay in Thailand for 4 months a year, and what type would they require?

As UK citizens, you and your wife can stay in Thailand for up to 4 months without a visa through visa-exempt entries. Typically, you can enter Thailand and receive a 60-day visa exemption, which can then be extended for an additional 30 days at an immigration office. If you exit and re-enter the country, you can obtain another 60-day exemption, thus facilitating a total of 4 months of stay within a single year. If your wife is a Thai citizen, she has no visa requirements. It's recommended to plan for potential border runs or extensions to manage your stay effectively.