Hi, I am 29 from the UK, and I will be marrying my girlfriend in March in Bangkok, we have a 7 month year old boy, I have bought land for her in Ubon and want to start building a house soon, can anyone tell me what my best options for a visa for long term stay in thailand.

Apply for a multiple entry Non-Immigrant 'O' Visa from the the Thai Consulate in either Birmingham or Hull. That'll enable you to stay for 90 days at a time. Once you are legally married, you can extend the visa for a year at a time provided you can comply with the financial obligations needed for support of a Thai spouse.