As a UK passport holder, do I need a return ticket to apply for a Non O visa to enter Thailand in January 2022.

My wife is Thai and we’ll return to Thailand from China, the plan being is for me to arrive with a Non O visa and apply for a ‘Married to a Thai’ long term visa after 30 days or so.

We have flights booked from China, although cannot get a return ticket, unless I book a one way ticket from Bangkok to London, although I’m not sure if I need to do this in order to get the Non O visa.

I would appreciate your feedback.