Even when you are married to your Thai wife, a uk visa will still be required before she wll be able to enter the UK. Being married will not automatically get your Thai wife a visa. If one of the main reasons of getting married is to get a visa easier, stop.
A Thai wife is able to get two main types of visa

Thai Wife UK Visitors Visa

A visitors visa is ideal for your wife to visit the UK, the amount of time issued on this type of visa is 6 months. While traveling to the UK with this visa, your wife will be allowed to stay in England as a tourist.

Thai Wife UK Tourist Visa

A UK Visitors visa in real terms is a UK Tourist visa.

Thai Wife UK Settlement Visa

A Thai wife UK Settlement visa is granted the first time for 2 year and 3 months. At the end of this time period you will have the opportunity to renew the Visa for another two years in the UK. The UK settlement visa will allow your Thai wife to live in the UK full time and to work.

All visas must be applied for at the British embassy in Bangkok.

Evidence will be needed at the time of the Thai wife UK Visa application.
Thai passport
Marriage certificate
Medical certificate