I found it better to email them with change of address and they responded but if you are already out of the UK then you need to go on the International pensions website
If you are both Non Thai's then you will need to show 800,000 each and possibly some to cover the Children too, if one of you is retirement age then it's possible to get a retirement visa showing just 800k the other partner could get a student visa to learn Thai and when that finishes ( usually 6 months) then 'follow' the retirement visa holder with a dependant visa.