You can apply to the British Embassy via the postal service and for an extra fee, the British Embassy will post back to you in Thailand. The alternative is that you can use the services of Key Visa who have been obtaining income verification letters for British citizens since the closure of the British Consulate in Pattaya. There is only a 300 baht service charge for the service offered and no hassle for you!
I am a British National and I require an income verification letter for my long stay visa, what should i do?
by Key Visa | Thai Visas