Does my Thai wife need to be a resident in Thailand for me to apply for a marriage visa while living in the UK?

You need to bring your wife every time you apply for a Non-O initial in-country visa or 1-year extension based on being married to a Thai national.

It's written, "In the case of spouse, the relationship must be de jure and de facto".

If your wife is not living in Thailand with you, your option will be

to apply for Non-O visa/extension based on being over 50 (retirement).

Or as you wrote, get a multiple entry Non-O spouse to a Thai national at the Thai consulate in Savannakhet with which you have to do a border-bounce every 90 days. Many people have this Non-O multiple.