I stayed in Thailand for more than 10 years on yearly visa extensions and I visited my home country Belgium every year for several weeks and enter Th again with a re entry permit . Due to medical treatment now I stayed in my home country for 6 months so I could not extend my existing visa and obtain a re entry visa . The immigration office gave me the advise to apply for a new non immigrant O visa 90 days in my country and then extend in my local Th immigration office . I fulfill al the requirements but I have one question :

When I apply for a non immigrant O visa on line , is it sufficient to buy or reserve a one way ticket or do I have to buy or reserve a return ticket .

One way sufficient