What visa do I need for two visits to Thailand, staying 1 month in June and 3 months starting December 26?

For a 1-month stay in June, you can enter Thailand on a tourist visa, which the immigration officer will stamp. You can extend this visa for another 30 days at a local immigration office for a fee of 1900 Thai baht. For your 3-month stay starting December 26, you can either continue to renew your stay through border runs (leaving Thailand and re-entering) or apply for a Non-O immigrant visa online, which is valid for 3 months and costs around £60. Consider researching more on Google or YouTube for detailed information.