Return flight date on a SETV.

[Cpattaya]

Hi there

I am retiring in May 2021, aged 50+ and I had plans to sort out my visa beforehand, either non O (in UK) or non O-A but everything has changed of course. I am now unsure how long i will stay in LOS on my first visit but maybe 3 or 4 months i am thinking now.  

I am intending flying over in mid May on a SETV which i believe is currently for 60 days and can be extended. 

My question is ..... "Will i be OK to book a flight which doesn't return to the UK for say 4 months when my visa will only technically last 60 days?" I would like to book now and start the trip planning rather than wait. I have only been out for 30 days at a time before.   

My long term aim is/was to change the above non O/OA to an extension of stay (based on retirement).  

Please advise. 

All help appreciated. 

Thank you