It is not true that obtaining a visa for a same sex partner or a transsexual is difficult. As long as the documents for a UK tourist visa are presented correctly, the British Embassy have no problems in awarding a visa to your same sex Thai partner. The British Embassy are in no way Homophobic and neither are the UK Immigration Authorities in the UK when your Thai partner arrives in the country. However, if the documentation is not provided in the correct way, the visa will be refused. This is why using a professional service is always the best option.