The same day. Or you can pay 1,900 for a 7 day extension.

I don't think he has a visa

A visa is just used to enter the country. Presumably you have an Extension of Stay. If so, this needs to be cancelled before you leave the country.

@Mark *******

She can get a Marriage Visitor visa which allows her to get married in the UK, but then she has to return to Thailand. My wife had this visa.

Have a good trip.

Contact

@Paul *******

for professional advice.

I think so. If you can prove you have been in a proper relationship for 2+ years. Settlement visas take a long time though, and you'll need the English test certificate and TB test before you apply.

I've done a UK Marriage Visitor visa as I married my wife in the UK, so feel free to PM me.

If there is a child too, and the child is not British, the financial requirements are higher.

There's no such thing as a UK Marriage visa. She can apply for a UK Marriage Visitor visa which allows her to marry in the UK but she has to return to Thailand. Alternatively she can apply for a settlement visa which means she can stay in the UK but for this you will need to meet the financial requirements (salary of at least £18,600, earned for 6 months before applying, or savings of £65,000). For this visa she would also need to pass the A1 English test, get a TB test and pay the NHS surcharge.