Hi, what type of visa do i need to stay in Thailand for 90 days, iam from uk. George

get a 60 day tourist visa and extend that for 30 days

Assuming you have not spent significant time in Thailand before, a single entry tourist visa (as described above) is the obvious choice. If you are near one of the honorary consulates, you can do this in person while you wait. Where do you live? Otherwise, you can use the misdescribed evisa system to get a visa from the London embassy.

60 day Visa by post from.UK Northern city...cant remember which one.

not my area but FWIW, Hull was easy, London was difficult, from someone passing through, not a UK citizen

1 hour ago, sunnyboy2018 said:

60 day Visa by post from.UK Northern city...cant remember which one.

You are probably thinking of Hull. That consulate is still good if applying in person, but postal applications to the honorary consulates is no longer allowed.